View allAll Photos Tagged cloudlike
My beautiful Smoke Tree is in full bloom now, with these light & fluffy cloud-like blooms! Best viewed large. I hope everyone is staying cool & healthy in this extreme heat we're experiencing!
M8 The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530
22 subs 5 min - 0 gain offset 50 -15*c
C-11 Hyperstar F/2 ZWO2600MC Pro
AP1100gto - unguided.
N.I.N.A beta capture - APP
"Postcard" 2 from The Cathedral of St. John the Divine. This time focusing on the sculptural, architectural forms of the Cathedral itself.
Some might read my "tumbling" of churches and cathedrals as "DE-structive", and while there is an element of questioning by radically altering the consensus view of the buildings, it's not meant to connote a criticism of the institution itself. Although I do believe that RE-viewing what these places mean and can do, is in order. But that only falls into the bigger picture of the major paradigm shift that calls the last 1,000 years of Western history into question.
So the "tumbled" cathedral instead, depicts, so to speak, a re-thinking or restructuring of the current view - definitely not it's destruction. A cathedral in the process of re-shaping itself.
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Music Link: "Lux Aeterna" - Gyorgy Ligeti, Hungarian composer. This haunting, evanescent, cloudlike music is largely remembered as one of the 3 Ligeti pieces that Stanley Kubrick used for his soundtrack to "2001: A Space Odyssey".
Ligeti's genius was in creating music as sheets of colour and tone ( timbre, in music ) through unconventional 'clustering' of notes and sonorities that shifted and moved indefinably at different times, 'wafting' through a kaleidoscope of sonic colours to create a powerful, weightless music that is unforgettable.
Although Ligeti was quite clear that this piece was not religious in nature, it nevertheless has a mystical quality to it that speaks of something beyond the every day.
www.youtube.com/watch?v=Zy8SQ-LWC20
Zoom in !!!
© Richard S Warner ( Visionheart ) - 2015. All Rights Reserved. This image is not for use in any form without explicit, express, written permission.
Scanned lith print.
Rollei Vintage 332 RC (?) found in a black plastic bag (who knows how long it has been in there?) and lith printed.
Very unfamiliar process results and outcome for this, so I may be questioning if that's the paper noted on the bag or not (or has it just gotten old?).
A very quick establishment of the print contours already after <30 sec, and then almost nothing happend... On some of the prints there's this wavy cloudlike pattern all over, not bad IMO (but it was not there on the negative).
Jan 8, 2022. Rolleiflex T w/ Tessar 75 mm/3.5 + yellow filter.
Fomapan 100 dev in Rodinal 1+100, semistand 1 h.
Lith printed on Rollei vintage 332 RC and developed in Moersch Easy Lith (25A+25B+H2Oqs750ml).
Toned in Se 1+9, 45 sec.
Conclusion: The Rollei Vintage 332 RC has been aging during the years so it's not a very good lith paper anymore.
Scanned lith print.
Rollei Vintage 332 RC (?) found in a black plastic bag (who knows how long it has been in there?) and lith printed.
Very unfamiliar process results and outcome for this, so I may be questioning myself if that's the paper noted on the bag or not (or has it just gotten old?).
A very quick establishment of the print contours already after <30 sec, and then almost nothing happend... On some of the prints there's this wavy cloudlike pattern all over, not bad IMO (but it was not there on the negative).
Jan 8, 2022. Rolleiflex T w/ Tessar 75 mm/3.5 + yellow filter.
Fomapan 100 dev in Rodinal 1+100, semistand 1 h.
Lith printed on Rollei vintage 332 RC and developed in Moersch Easy Lith (25A+25B+H2Oqs750ml).
Toned in Se 1+9, 45 sec.
Conclusion: The Rollei Vintage 332 RC has been aging during the years so it's not a very good lith paper anymore.
This picture is not exactly sharp, since I caught this sweet little thing, dancing in the cool breeze of the evening. I was mildly amused with the background forming cloudlike patterns.
Scanned lith print.
Rollei Vintage 332 RC (?) found in a black plastic bag (who knows how long it has been in there?) and lith printed.
Very unfamiliar process results and outcome for this, so I may be questioning if that's the paper noted on the bag or not (or has it just gotten old?).
A very quick establishment of the print contours already after <30 sec, and then almost nothing happend... On some of the prints there's this wavy cloudlike pattern all over, not bad IMO (but it was not there on the negative).
Jan 8, 2022. Rolleiflex T w/ Tessar 75 mm/3.5 + yellow filter.
Fomapan 100 dev in Rodinal 1+100, semistand 1 h.
Lith printed on Rollei vintage 332 RC and developed in Moersch Easy Lith (25A+25B+H2Oqs750ml). Feb 1, 2025.
Toned in Se 1+9, 45 sec.
Conclusion: The Rollei Vintage 332 RC has been aging during the years so it's not a very good lith paper anymore.
This was the first print in fresh soup. Took about 40 min (!) to be "ready" and still not defined...
Se toning was good and shifted the color tone to "blue metallic".
Yikes, not sure if I have the stamina for this, but the blue-stealish image tone after Se-toning was a reward.
LRGB composition with frames recorded by Eric Recurt in Tenerife with his 350mm F3.3 and FLI16803.
L: 21x300s
RGB: (5, 5, 5)x300s
Copyright: R. Colombari / E. Recurt
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The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654[4] and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
Source: Wikipedia
The tree of enlightenment was tall and outstanding. Its trunk was diamond, its main boughs were lapiz lazuli, its branches and twigs were of various precious elements. The leaves, spreading in all directions, provided shade, like clouds. The precious blossoms were of various colors, the branching twigs spread out their shadows. Also the fruits were jewels containing a blazing radiance. They were together with the flowers in great arrays. The entire circumference of the tree emanated light; within the light there rained precious stones, and within each gem were enlightening beings, in great hosts like clouds, simultaneously appearing. The palace chamber in which the Buddha was situated was spacious and beautifully adorned. It extended throughout the ten directions. It was made of jewels of various colors and was decorated with all kinds of precious flowers. The various adornments emanated lights like clouds; the masses of their reflections from within the palace formed banners.
A boundless host of enlightening beings, the congregation at the site of enlightenment, were all gathered there: by means of the ability to manifest the lights and inconceivable sounds of the Buddhas, they fashioned nets of the finest jewels, from which came forth all the realms of action of the spiritual powers of the Buddhas, and in which were reflected images of the abodes of all beings.
Clouds of radiance of jewels reflected each other: the Buddhas of the ten directions conjured regal pearls, and exquisite jewels in the topknots of all the enlightening beings all emanated light, which came and illuminated them.
At that time, the Buddha, the World Honored One, in this setting, attained to the supreme, correct awareness of all things. His knowledge entered into all times with complete equanimity; his body filled all worlds; his voice universally accorded with all lands in the ten directions. Like space, which contains all forms, he made no discrimination among all objects. And, as space extends everywhere, he entered all lands with equanimity. His body forever sat omnipresent in all sites of enlightenment. Among the hosts of enlightening beings, his awesome light shone clearly, like the sun emerging, illumining the world. The ocean of myriad virtues which he practiced in all times was thoroughly pure, and he constantly demonstrated the production of all the buddha-lands, their boundless forms and spheres of light extending throughout the entire cosmos, equally and impartially.
He expounded all truths, like spreading great clouds. Each of his hairtips was able to contain all worlds without interference, in each manifesting immeasurable spiritual powers, teaching and civilizing all spiritual beings. His body extended throughout the ten directions, yet without coming or going. His knowledge entered into all forms and realized the emptiness of all things. All the miraculous displays of the Buddhas of past, present, and future, were all seen in his light, and all the adornments of inconceivable eons were revealed.
There were great enlightenment beings numerous as the atoms in ten buddha-worlds surrounding him. Their names were: Universally Good (Samantabhadra), Light of the Supreme Lamp of Universal Virtue, Lion Banner of Universal Light, Subtle Light of Flames of Universal Jewels, Banner of Oceans of Qualities of Universal Sounds, Realm of Enlightenment of Radiance of Universal Knowledge, Banner of Flowers of a Topknot of Universal Jewels, Pleasing Voice of Universal Awareness, Light of Inexhaustible Virtue of Universal Purity, Mark of Universal Light, Great Brilliance of the Light of the Moon Reflected in the Ocean, Undefiled Treasury of Light of Oceans of Cloudlike Sounds, Born of Wisdom and Adorned with Virtue, Great Light of Sovereign Virtue, Brave Lotus Topknot, Sun Banner of Clouds of Universal Knowledge, Greatly Persevering with Indestructible Courage, Light Banner of Fragrant Flames, Deep Beautiful Sound of Great Enlightened Virtue, Born of Wisdom with the Light of Great Virtue. These and others were the leaders — there were as many as there are atoms in ten buddha-worlds.
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Photographed at Algonquin Provincial Park, Ontario, Canada
between 21.19 and 21.53 EDT
(285 km by road north of Toronto)
* Altitude of M8 at time of exposures: 21°, decreasing to 19°
* Temperature 11° C.
* Total exposure time: 15 minutes
* 1200 mm focal length telescope
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Description:
Low in the northern hemisphere summer sky is the large Lagoon Nebula in the constellation Sagittarius (The Archer). The Lagoon (also known as Messier 8 or M8) is a favourite target of amateur astronomers with modest telescopes. The red colour - which the human eye can't detect - is the telltale sign of ionized hydrogen gas clouds.
From Wikipedia:
"The Lagoon Nebula ... is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. ... The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material) ... It also includes a funnel-like or tornado-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula."
Embedded in the nebula - and just to left of its centre in this view - is the bright star cluster NGC 6530. Several dark globules are quite readily visible as well.
To see a wider angle view of this nebula and other adjacent objects, click here:
www.flickr.com/photos/97587627@N06/28874267555
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Nikon D810a camera body on Explore Scientific 152 mm (6") apochromatic refracting telescope, mounted on Astrophysics 1100GTO equatorial mount with a Kirk Enterprises ball head
Fifteeen stacked subframes; each frame:
ISO 3200; 1 minute exposure at f/8
(with LENR - long exposure noise reduction)
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (brightness, contrast, levels, colour balance, sharpening)
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Photographed at Algonquin Provincial Park, Ontario, Canada
between 00.28 and 00.54 EDT
(285 km by road north of Toronto)
* Altitude of centre of frame at time of exposures: ~19°
* Temperature 7° C.
* Total exposure time: 12 minutes
* 660 mm focal length telescope
___________________________________________
Description:
M8, the Lagoon Nebula (right side of the frame)
One of the most prominent, large, bright and well known nebulae in the sky is the Lagoon Nebula (M8), which is a favourite target of amateur astronomers with modest telescopes.
From Wikipedia: "The Lagoon Nebula ... is a giant interstellar cloud ... classified as an emission nebula and as an H II region. [It] was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years away from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. ... The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296."
M20, the Trifid Nebula (upper left side of the frame)
Lying just to the north of the large Lagoon Nebula is M20, the Trifid Nebula in the constellation Sagittarius (The Archer). The Trifid is unusual in consisting of both a red emission nebula (ionized hydrogen gas) and a fainter blue reflection nebula. It lies about 5,200 light years from our solar system.
From Wikipedia:
"The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) is an H II region located in Sagittarius. It was discovered by Charles Messier on June 5, 1764. Its name means 'divided into three lobes'. The object is an unusual combination of an open cluster of stars; an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent 'gaps' within the emission nebula that cause the trifurcated appearance; these are also designated Barnard 85). Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.
The Trifid Nebula is a star-forming region in the Scutum spiral arm of the Milky Way. The most massive star that has formed in this region is HD 164492A, an O7.5III star with a mass more than 20 times the mass of the Sun. This star is surrounded by a cluster of approximately 3100 young stars."
To the lower left of the Trifid is the open star cluster M21.
For a version of this photo WITH LABELS, click on the RIGHT side of your screen, or click here:
www.flickr.com/photos/97587627@N06/50019465117
To see a wider angle view this and other adjacent nebulae, photographed in Australia in Sept. 2019, click here:
www.flickr.com/photos/97587627@N06/49183970671
__________________________________________
Technical information:
Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic astrograph, mounted on Astrophysics 1100GTO equatorial mount
Twelve stacked frames; each frame:
660 mm focal length
ISO 2500; 1 minute exposure at f/5.2; unguided
With long exposure noise reduction
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (levels, brightness / contrast, colour desaturation, sharpening)
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M8 The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530
22 subs 5 min - 0 gain offset 50 -15*c
C-11 Hyperstar F/2 ZWO2600MC Pro
AP1100gto - unguided.
N.I.N.A beta capture - DeepSkyStacker.
362 | 365
"We'll begin with a spin, traveling in a world of my creation. What we'll see will defy explanation.
There is no life I know to compare to pure imagination. Living there, you'll be free if you truly wish to be." - Willy Wonka
Listen: www.youtube.com/watch?v=9BkBGdnUNSk
[I'm more than a little obsessed with Fiona's cover of the classic Pure Imagination from the old-school Willy Wonka and the Chocolate Factory. I can't stop listening to it. I had the absolute joy of seeing Fiona in concert a few weeks ago here in Seattle. I don't think I love another woman on this planet quite so much as her. She is brilliant. And sincere. The sincerity is what really gets me. There just isn't *enough* of that in the world. Honesty. Sincerity. Being straightforward. It *matters*.
For this image I covered myself in musty Value Village pillow stuffing and also shoved it in my mouth. Makes this pic a bit less dreamy, huh? Sometimes you gotta do what you gotta do. Thank you to Austin for being just as anal as me in assisting with this image!]
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Photographed at Algonquin Provincial Park, Ontario, Canada
between 01.18 and 01.42 EDT
(285 km by road north of Toronto)
* Altitude of centre of frame at time of exposures: ~19°
* Temperature 14° C.
* Total exposure time: 12 minutes
* 660 mm focal length telescope
___________________________________________
Description:
M8, the Lagoon Nebula (right side of the frame)
One of the most prominent, large, bright and well known nebulae in the sky is the Lagoon Nebula (M8), which is a favourite target of amateur astronomers with modest telescopes.
From Wikipedia: "The Lagoon Nebula ... is a giant interstellar cloud ... classified as an emission nebula and as an H II region. [It] was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years away from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. ... The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296."
M20, the Trifid Nebula (upper left side of the frame)
Lying just to the north of the large Lagoon Nebula is M20, the Trifid Nebula in the constellation Sagittarius (The Archer). The Trifid is unusual in consisting of both a red emission nebula (ionized hydrogen gas) and a fainter blue reflection nebula. It lies about 5,200 light years from our solar system.
From Wikipedia:
"The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) is an H II region located in Sagittarius. It was discovered by Charles Messier on June 5, 1764. Its name means 'divided into three lobes'. The object is an unusual combination of an open cluster of stars; an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent 'gaps' within the emission nebula that cause the trifurcated appearance; these are also designated Barnard 85). Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.
The Trifid Nebula is a star-forming region in the Scutum spiral arm of the Milky Way. The most massive star that has formed in this region is HD 164492A, an O7.5III star with a mass more than 20 times the mass of the Sun. This star is surrounded by a cluster of approximately 3100 young stars."
To the lower left of the Trifid is the open star cluster M21.
For a version of this photo WITH LABELS, click on the RIGHT side of your screen, or click here:
www.flickr.com/photos/97587627@N06/52266017684
To see a wider angle view this and other adjacent nebulae, photographed in Australia in Sept. 2019, click here:
www.flickr.com/photos/97587627@N06/49183970671
__________________________________________
Technical information:
Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic telescope, mounted on Astrophysics 1100GTO equatorial mount
Twelve stacked frames; each frame:
660 mm focal length
ISO 4000; 1 minute exposure at f/5.2; unguided
With long exposure noise reduction
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (levels, brightness / contrast, colour balance)
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Photographed at Algonquin Provincial Park, Ontario, Canada
between 02.24 and 02.44 EDT
(285 km by road north of Toronto)
* Altitude of centre of frame at time of exposures: ~12°
* Temperature 14° C.
* Total exposure time: 10 minutes
* 660 mm focal length telescope
___________________________________________
Description:
North is to the upper right in this image, which contains several objects of note.
M8, the Lagoon Nebula, with embedded star cluster NGC 6530 (right side of the frame)
One of the most prominent, large, bright and well known nebulae in the sky is the Lagoon Nebula (M8), which is a favourite target of amateur astronomers with modest telescopes.
From Wikipedia: "The Lagoon Nebula ... is a giant interstellar cloud ... classified as an emission nebula and as an H II region. [It] was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years away from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. ... The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296."
IC 4678 (directly above M8)
This is a tiny nebula composed of emission (pink) and reflection (blue) components.
NGC 6544 (near centre of frame)
This is a small globular star cluster of magnitude ~7.3, lying at a distance of 9,000-10,00 light years from us..
NGC 6553 (left edge of frame, just below centre)
This is a globular star cluster of magnitude ~8.@, with an unusually low star concentration even at its centre, and lying about 19,600 LY from our solar system. Studies show that it underwent two distinct periods of star formation, resulting in two populations of stars with differing compositions, especially in sodium and aluminum.
For a version of this photo WITH LABELS, click on the RIGHT side of your screen, or click here:
www.flickr.com/photos/97587627@N06/52229322166
To see a wider angle view this and other adjacent nebulae, photographed in Australia in Sept. 2019, click here:
www.flickr.com/photos/97587627@N06/49183970671
__________________________________________
Technical information:
Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic telescope, mounted on Astrophysics 1100GTO equatorial mount
Ten stacked frames; each frame:
660 mm focal length
ISO 2500; 1 minute exposure at f/5.2; unguided
With long exposure noise reduction
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (levels, brightness / contrast, colour balance)
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Messier 8 The Lagoon Nebula
The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years away from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears pink in time-exposure color photos but is gray to the eye peering through binoculars or a telescope, human vision having poor color sensitivity at low light levels. The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel), which should not be confused with the better known Engraved Hourglass Nebula in the constellation of Musca. In 2006 the first four Herbig–Haro objects were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it. (Wikipedia.org)
Technical Information for This Image
This image was taken with a William Optics Zenithstar 81 APO Doublet Refractor on an iOptron CEM25P mount. This telescope is a very compact unit and has optical elements made of FPL53 glass and is actually considerably sharper than some of my larger telescopes. The main imaging camera, attached to the prime focus of the telescope was a ZWO ASI294MC Pro cooled camera which was cooled to -5C. The 19 exposures were each 240 seconds, and the gain was set to 120. An Optolong L-Pro filter was used in capturing the exposures. Auto guiding was done using a Skywatcher EVO Guide 50mm refractor attached to a ZWO ASI290MC camera which was connected to PHD2 autoguiding software. Capturing was done with Astrophotography Tool (APT) software and post processed with Pixinsight software with finishing touches put in using Adobe Photoshop Creative Cloud. Polar Alignment for the evening was done using SharpCap software.
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Photographed 4.5 km north of (13 km by road from) Uluru-Kata Tjuta National Park (Ayers Rock), Northern Territory, Australia, between 22.00 and 22.15 CAST (Central Australia Standard Time)
* Observing site: Long. 131.07° E. | Lat. 25.22° S. | Elev. 501 m
* Altitude of centre of nebula at time of exposures: ~55°
* Total exposure time: 14 minutes
* 660 mm focal length telescope
___________________________________________
Description:
One of the most prominent, largest, brightest and well known nebulae in the sky is the Lagoon Nebula, which is a favourite target of amateur astronomers with modest telescopes.
From Wikipedia: "The Lagoon Nebula ... is a giant interstellar cloud ... classified as an emission nebula and as an H II region. [It] was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years away from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. ... The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296."
For a version of this photo WITH LABELS, click on your screen to the RIGHT of the photo, or click here:
www.flickr.com/photos/97587627@N06/49279607658
Here is a photo of the gear that used for astrophotography on this trip:
www.flickr.com/photos/97587627@N06/49017804808
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Technical information:
Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic astrograph, mounted on iOptron CEM40 equatorial mount
Fourteen stacked subframes - each frame:
ISO 5000; 1 minute exposure at f/5.2, 660 mm focal length, unguided
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (brightness, contrast, levels, colour balance)
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This image was produced from data captured by Dave Frost at the Chesterfield Observatory in the UK.
I have added an image of the Earth just above the Sun so that you can get a feel for how big the Sun is.
Despite its enormity, the Sun is only a small star and classified as a Yellow Dwarf. There are stars so large out there – such as VY Canis Majoris and UY Scuti – that they make the Sun look like a tiny marble on the Moon. UY Scuti is so big that 5 billion Suns could fit in it!
This image was captured in black and white and then I used a process of colourising and inversion to create the final image.
The temperature on and just above the surface of the Sun changes dramatically depending on what’s happening. In this image, the lighter something appears, the cooler it is. The vast majority of the surface has a temperature of around 5500 degrees centigrade. Just above the centre and to the right there is a complex area of dark and light/hot and cool features. The white dots are sunspots; small dips in the surface caused by local magnetic activity. Did I say small? By comparison to the Sun yes but compared to the Earth? You can see from the size of the Earth at the top that these things are huge!
These features are typically around 1500° C cooler than the rest of the surface. However, there are dark areas around sunspots called plage (pronounced plarj) which is hot plasma mostly seen around sunspots although it is sometimes seen before a sunspot forms and might remain for a while after a sunspot disappears. Sunspots are transient features that typically live for a number of weeks. Their depth is not known with any certainty but they are currently thought to be about 4 mm’s deep.
We don’t yet know enough about plage to explain it properly. In fact, we continue to have many unanswered questions about the Sun because it is such a hostile place. There's a space probe called Parker that is going to get as close to the Sun as just 4.3 million miles (6.9 million km). I'm sure Parker will give some answers to the many scientific questions that remain unanswered about the Sun. When Parker gets to its top speed it will hit 430,000 mph which by anyone’s standard is quite nippy.
Around the edge of the Sun you can see cloudlike features that are called prominences. There’s a beautiful prominence at the very top pointing towards the image of the Earth. You can see that it dwarfs the Earth dramatically.
A prominence is plasma (very hot gas) that has escaped the surface of the Sun but is then pulled back onto it by a local strong magnetic field produced by the Sun.
Take a moment to consider this. Look at how big it is compared to the Earth. The Earth’s diameter is 12,742km or 7,918 miles so that makes the height of the prominence around 4 times that at 48,000 km but that’s just the visible part in this image.
There will be more plasma above and around it that either hasn’t been captured because it’s too faint or because my image processing has removed it.
Light wisps of gas seem to float over the surface. These are called filaments and they are prominences by another name because of where we see them.
Gas climbs to the surface of the Sun in huge capsules called granules and the surface is a swirling mass of plasma that burns or escapes and then gets replenished by other granules. Despite all this activity and all the stuff emitted by the Sun, its mass reduces very slowly. The rate? About 600 million tons per second.
Look at the area just below 9 o’clock and out far to the left of the Sun. You can see a barely perceptible wisp of plasma that is a Coronal Mass Ejection (CME). Despite its meagre appearance, this is a very powerful feature that has escaped the Sun and is roaring into space.
The biggest know CME to ever reach and impact the Earth is known as the Carrington Event of 1859 which caused telegraph stations across Europe and North America to malfunction. Some stopped working, some caught fire, some gave operators electric shocks and some equipment even came back to life using the Sun’s electricity to send phantom messages. If we had a Carrington Event in the modern era who knows how much harm it would do to our electricity-centric world.
The Sun forms a protective bubble around the solar system shielding everything in it from harmful interstellar rays. It holds us in orbit with its incredibly powerful gravity. It gives us heat and light. The Sun gives life with all its goodness but prevents it from existing in most parts of the solar system due to the poisonous nature of the solar winds which we are thankfully protected from by the Earth's magnetic field.
Fortunately we are in a good spot just 93 million miles from the Sun in what is called the habitable zone where water can exist in liquid form. We are lucky. The Sun will continue to exist long after our time on this planet has gone. Perhaps by then we’ll have worked out how to leave Earth and inhabit some other place.
The Sun is getting hotter and will continue to do so throughout the remainder of its life. Eventually the heat will cause all water to disappear and Earth will become a barren place but that won’t happen for about a billion years.
Images like this take a lot of processing. They are derived from video. When you take a picture of something, only a certain amount of light reaches your camera's sensor. Open the shutter for longer and you let more light in. Eventually, the image becomes over exposed and useless.
Each frame of your video captures a certain amount of light that, if your settings are right, will have a good exposure. Imagine stacking one frame on top of another until the whole video is seen through what looks like one frame. Each image will have captured different light waves and that means your stack of images contains and so shows a whole lot more detail than one frame would.
Of course this won’t make any difference for say, a beautiful landscape on a clear day but the Sun is constantly bubbling away and emitting light at different strengths from different (albeit only fractionally) light sources and this means that stacking all your video frames together will ultimately show a lot more detail on and just above the Sun’s surface. A piece of software such as Registax or Deep Sky Stacker or AutoStakkert or a feature in Photoshop does that stacking but it is really clever and very selective about how it stacks the image to ultimately produce a brilliant result which is a single picture with (if you’ve done it right) lots of detail like in this picture.
At this stage the image is black and white. I could leave it this way as I have on some of my pictures as you can see in my Photostream but there’s a slight disadvantage to this – the ‘dynamic range’ is not great and this means the shades of grey on and near the surface of the Sun are quite similar. Lots of solar imagers choose to colour the Sun red because that’s what it looks like through the solar telescope that uses a filter to focus on light in the red part of the spectrum. Sometimes you might see blue images and they have been captured using a Calcium-K solarscope which only looks at light emitted in the blue part of the spectrum specifically at the wavelength of 393 nanometres.
However, using the technique I have in this image gives the details a bit more differentiation and a bit of a 3D feel. The simple way to describe it is ‘solar inversion’ which is a fair description but not entirely true because I invert my images slightly differently to some other imagers. It’s not really challenging to create an image like this but you have to take your time and make sure everything looks right when you finish off.
So if you have read through this very long description, you might still have a question and that is why have I coloured the Sun in gold and not yellow? Well, it seems that people generally choose gold and I suspect it’s because it creates better contrast and so helps that 3D look emerge. I always play around with the final shade of gold so that I can get a result that I like. On this occasion I’ve given it a yellowish tint.
But what of the Sun’s real colour? Is it yellow? No. That’s weird right? I mean, why would you classify the Sun as a Yellow Dwarf star if it’s not yellow? Is it gold? No. So some other shade similar to yellow? No, forget yellow. If you want to see the real colour of the Sun you have to go into space. Away from the Earth’s atmosphere, the Sun looks white. If you take the average colour of all light emitted by the Sun, you get white. So we should call it a White Dwarf, right? Well, no we can’t call it that because something else already has that name. Maybe I’ll explain what that is another time…
Editor's note: Hey, thanks for letting me know this had made Explore, everyone! Really appreciate all the comments and traffic on on images. Y'all are the best Flickr friends ever! :)
This photograph of polar mesospheric clouds was acquired at an altitude of just over 202 nautical miles (about 322 kilometers) in the evening hours (03:19:54 Greenwich Mean Time) on Aug. 2, 2011, as the International Space Station was passing over the English Channel. The nadir coordinates of the station were 49.1 degrees north latitude and 5.5 degrees west longitude. Polar mesospheric clouds (also known as noctilucent, or "night-shining" clouds) are transient, upper atmospheric phenomena that are usually observed in the summer months at high latitudes (greater than 50 degrees) of both the Northern and Southern Hemispheres. They appear bright and cloudlike while in deep twilight. They are illuminated by sunlight when the lower layers of the atmosphere are in the darkness of Earth's shadow. The horizon of Earth appears at the bottom of the image, with some layers of the lower atmosphere already illuminated by the rising sun. The higher, bluish-colored clouds look much like wispy cirrus clouds, which can be found as high as 60,000 feet (18 kilometers) in the atmosphere. However noctilucent clouds, as seen here, are observed in the mesosphere at altitudes of 250,000 to 280,000 feet (about 76 to 85 kilometers). Astronaut observations of polar mesospheric clouds over northern Europe in the summer are not uncommon.
Image credit: NASA
Original image:
spaceflight.nasa.gov/gallery/images/station/crew-28/html/...
More about space station research:
www.nasa.gov/mission_pages/station/research/index.html
There's a Flickr group about Space Station Research. Please feel welcome to join! www.flickr.com/groups/stationscience/
View almost 400 photos like this in the "NASA Earth Images" Flickr photoset:
M8 - Lagoon Nebula
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654[4] and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654[4] and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
Lum 60x120sec.
RGB 120X120sec Each.
Data from deepskywest.com/
"Foam" sculpture by Kohei Nawa. Part of the Fukami exhibition (2018) at the Hôtel Salomon de Rothschild, Paris
© All Rights Reserved. Please do not use or reproduce this image on Websites/Blog or any other media without my explicit permission.
It's a clear night along the shore of Bear Lake as 15 minutes of rotation is taken in by my camera. The galactical core is but a cloudlike feature in a starlit sky that is streaking in front of us at around 1000mph.
Through the thick smoke layer the sun was a safe target. I was surprised that the image brought out some sunspots.
"Foam" sculpture by Kohei Nawa. Part of the Fukami exhibition (2018) at the Hôtel Salomon de Rothschild, Paris
Color my world daily - Friday: Blue
© All Rights Reserved. Please do not use or reproduce this image on Websites/Blog or any other media without my explicit permission.
M8 The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530
22 subs 5 min - 0 gain offset 50 -15*c
C-11 Hyperstar F/2 ZWO2600MC Pro
AP1100gto - unguided.
N.I.N.A beta capture - DeepSkyStacker.
Hope everyone is enjoying Thursday~
I was taking some final shots of a few fading flowers yesterday and I really liked this one...cropped to just this single bud...the cloud like bokeh are more baby's breath... =) It looked heavenly to me once I viewed from my camera to big screen...hope you enjoy!
I don't know if that was Aurora but I never changed shape or shifted in colour.
There are three luminous objects in this photo. The Orange glow is Twilight and green glow is the Aurora and the Last is the Noctilucent cloud that formed in between the two.
I later found out through a flickr friend it was a Noctilucent cloud.
'Noctilucent clouds, also known as polar mesospheric clouds, are bright cloudlike atmospheric phenomena visible in a deep twilight. The name means roughly "night shining" in Latin. They are most commonly observed in the summer months at latitudes between 50° and 70° north and south of the equator.'
The huge mosaic released by ESA’s Euclid space telescope on 15 October 2024 accounts for 1% of the wide survey that Euclid will capture over six years. The location and actual size of the mosaic on the Southern Sky is shown in yellow.
This all-sky view is an overlay of ESA Gaia’s star map from its second data release in 2018 and ESA Planck’s dust map from 2014.
[Image description: A dark blue oval image, with a bright band spanning from left to right, from which light blue clouds of smoke appear to be seeping into the rest of the shape. This bright band is interrupted by darker cloudlike structures. In the lower right of the oval there is a small patch marked in bright yellow, which indicates the area of the full mosaic in context of this global map of our Milky Way galaxy.]
Credits: ESA/Euclid/Euclid Consortium/NASA; ESA/Gaia/DPAC; ESA/Planck Collaboration; CC BY-SA 3.0 IGO
Designer Ellen Kennon: "I'll do entire houses in Mushroom, which is pretty darned fabulous. It's a beige, but it changes drastically — one minute it's putty and the next, it's rosier. Chameleon-like and mysterious, it takes on the properties of the colors around it. You want to put your hand out and touch the wall because it doesn't look solid. It's almost cloudlike." Photo from House Beautiful.
The massive scale of the Arche is most obvious in its atrium, which hosts a parasitic stretched Teflon mesh called The Cloud. This portion of the building was an afterthought added to the project once Paul Andreau took over the project. The innovative awning allows wind and light to permeate, while shielding visitors from the elements. This seemingly cloudlike structure is fastened by tensioned cables which clutches onto the building’s façade, and whose figure appears alien like among the sharp contours of the Grande Arche. (from Archdaily)
Đến với Meera Meera Fashion Concept, chúng tôi không chỉ đơn thuần may một chiếc áo cưới mà đó là công việc thực hiện giấc mơ cho mọi cô dâu. Mời bạn nhìn ngắm thiết kế cổ tích sau đây:
Một chiếc váy cưới sang trọng đầy tinh tế trong từng chi tiết cầu kỳ: Dáng công chúa với đường cắt hạ eo sẽ làm nổi bật sắc vóc của bạn; trong khi vải lưới và ren Chantilly đính kết là sự kết hợp vượt thời gian, thực sự làm xiêu lòng bất kỳ người đẹp nào.
Cúp áo cổ chữ V xẻ sâu táo bạo lại đồng thời tôn lên vẻ lãng mạn của thân áo tay ren dài trang trọng, điểm xuyết trên đó là những hoạ tiết ren Chantilly tinh xảo.
Và thử tưởng tượng xem - Còn ai có thể toát lên khí chất kiêu sa như bạn khi diện lên người chiếc áo cưới với tùng váy lưới xoè dài lộng lẫy, mà lại nhẹ tênh đến như vầy. Ắt hẳn bạn đã chờ đợi giây phút 'Say Yes' này rất lâu rồi đúng không nào?
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Không may sẵn, cho thuê.
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The Light appeared around midnight.
There are three luminous objects in this photo. The Orange glow is Twilight and green glow is the Aurora and the Last is the Noctilucent cloud that formed in between the two.
Noctilucent clouds, also known as polar mesospheric clouds, are bright cloudlike atmospheric phenomena visible in a deep twilight. The name means roughly "night shining" in Latin. They are most commonly observed in the summer months at latitudes between 50° and 70° north and south of the equator.
Comet Neowise on 14 July 2020, Burke, Virginia; Canon 60D camera and 75-200mm lens; single frame.
From Wikipedia
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times Earth's diameter, while the tail may stretch beyond one astronomical unit. If sufficiently bright, a comet may be seen from Earth without the aid of a telescope and may subtend an arc of 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures and religions.
Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars and the galactic tide. Hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition.
Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma (the central part immediately surrounding the nucleus) and the tail (a typically linear section consisting of dust or gas blown out from the coma by the Sun's light pressure or outstreaming solar wind plasma). However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. The discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. In the early 21st century, the discovery of some minor bodies with long-period comet orbits, but characteristics of inner solar system asteroids, were called Manx comets. They are still classified as comets, such as C/2014 S3 (PANSTARRS). 27 Manx comets were found from 2013 to 2017.
As of November 2021 there are 4584 known comets. However, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System (in the Oort cloud) is estimated to be one trillion. Roughly one comet per year is visible to the naked eye, though many of those are faint and unspectacular. Particularly bright examples are called "great comets". Comets have been visited by unmanned probes such as the European Space Agency's Rosetta, which became the first to land a robotic spacecraft on a comet, and NASA's Deep Impact, which blasted a crater on Comet Tempel 1 to study its interior.
A comet was mentioned in the Anglo-Saxon Chronicle that allegedly made an appearance in 729 AD.
The word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a romanization of the Greek κομήτης 'wearing long hair', and the Oxford English Dictionary notes that the term (ἀστὴρ) κομήτης already meant 'long-haired star, comet' in Greek. Κομήτης was derived from κομᾶν (koman) 'to wear the hair long', which was itself derived from κόμη (komē) 'the hair of the head' and was used to mean 'the tail of a comet'.
The astronomical symbol for comets (represented in Unicode) is U+2604 ☄ COMET, consisting of a small disc with three hairlike extensions.
The core structure of a comet is known as the nucleus. Cometary nuclei are composed of an amalgam of rock, dust, water ice, and frozen carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are popularly described as "dirty snowballs" after Fred Whipple's model. Comets with a higher dust content have been called "icy dirtballs". The term "icy dirtballs" arose after observation of Comet 9P/Tempel 1 collision with an "impactor" probe sent by NASA Deep Impact mission in July 2005. Research conducted in 2014 suggests that comets are like "deep fried ice cream", in that their surfaces are formed of dense crystalline ice mixed with organic compounds, while the interior ice is colder and less dense.
The surface of the nucleus is generally dry, dusty or rocky, suggesting that the ices are hidden beneath a surface crust several metres thick. In addition to the gases already mentioned, the nuclei contain a variety of organic compounds, which may include methanol, hydrogen cyanide, formaldehyde, ethanol, ethane, and perhaps more complex molecules such as long-chain hydrocarbons and amino acids. In 2009, it was confirmed that the amino acid glycine had been found in the comet dust recovered by NASA's Stardust mission. In August 2011, a report, based on NASA studies of meteorites found on Earth, was published suggesting DNA and RNA components (adenine, guanine, and related organic molecules) may have been formed on asteroids and comets.
The outer surfaces of cometary nuclei have a very low albedo, making them among the least reflective objects found in the Solar System. The Giotto space probe found that the nucleus of Halley's Comet (1P/Halley) reflects about four percent of the light that falls on it, and Deep Space 1 discovered that Comet Borrelly's surface reflects less than 3%; by comparison, asphalt reflects seven percent. The dark surface material of the nucleus may consist of complex organic compounds. Solar heating drives off lighter volatile compounds, leaving behind larger organic compounds that tend to be very dark, like tar or crude oil. The low reflectivity of cometary surfaces causes them to absorb the heat that drives their outgassing processes.
Comet nuclei with radii of up to 30 kilometers (19 mi) have been observed, but ascertaining their exact size is difficult. The nucleus of 322P/SOHO is probably only 100–200 meters (330–660 ft) in diameter. A lack of smaller comets being detected despite the increased sensitivity of instruments has led some to suggest that there is a real lack of comets smaller than 100 meters (330 ft) across. Known comets have been estimated to have an average density of 0.6 g/cm3 (0.35 oz/cu in). Because of their low mass, comet nuclei do not become spherical under their own gravity and therefore have irregular shapes.
Roughly six percent of the near-Earth asteroids are thought to be the extinct nuclei of comets that no longer experience outgassing, including 14827 Hypnos and 3552 Don Quixote.
Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals.[33][34] Further, the ALICE spectrograph on Rosetta determined that electrons (within 1 km (0.62 mi) above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.[35][36] Instruments on the Philae lander found at least sixteen organic compounds at the comet's surface, four of which (acetamide, acetone, methyl isocyanate and propionaldehyde) have been detected for the first time on a comet.[37][38][39]
The streams of dust and gas thus released form a huge and extremely thin atmosphere around the comet called the "coma". The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous "tail" to form pointing away from the Sun.[48]
The coma is generally made of water and dust, with water making up to 90% of the volatiles that outflow from the nucleus when the comet is within 3 to 4 astronomical units (450,000,000 to 600,000,000 km; 280,000,000 to 370,000,000 mi) of the Sun.[49] The H2O parent molecule is destroyed primarily through photodissociation and to a much smaller extent photoionization, with the solar wind playing a minor role in the destruction of water compared to photochemistry.[49] Larger dust particles are left along the comet's orbital path whereas smaller particles are pushed away from the Sun into the comet's tail by light pressure.[50]
Although the solid nucleus of comets is generally less than 60 kilometers (37 mi) across, the coma may be thousands or millions of kilometers across, sometimes becoming larger than the Sun.[51] For example, about a month after an outburst in October 2007, comet 17P/Holmes briefly had a tenuous dust atmosphere larger than the Sun.[52] The Great Comet of 1811 also had a coma roughly the diameter of the Sun.[53] Even though the coma can become quite large, its size can decrease about the time it crosses the orbit of Mars around 1.5 astronomical units (220,000,000 km; 140,000,000 mi) from the Sun.[53] At this distance the solar wind becomes strong enough to blow the gas and dust away from the coma, and in doing so enlarging the tail.[53] Ion tails have been observed to extend one astronomical unit (150 million km) or more.[52]
Both the coma and tail are illuminated by the Sun and may become visible when a comet passes through the inner Solar System, the dust reflects sunlight directly while the gases glow from ionisation.[54] Most comets are too faint to be visible without the aid of a telescope, but a few each decade become bright enough to be visible to the naked eye.[55] Occasionally a comet may experience a huge and sudden outburst of gas and dust, during which the size of the coma greatly increases for a period of time. This happened in 2007 to Comet Holmes.[56]
In 1996, comets were found to emit X-rays.[57] This greatly surprised astronomers because X-ray emission is usually associated with very high-temperature bodies. The X-rays are generated by the interaction between comets and the solar wind: when highly charged solar wind ions fly through a cometary atmosphere, they collide with cometary atoms and molecules, "stealing" one or more electrons from the atom in a process called "charge exchange". This exchange or transfer of an electron to the solar wind ion is followed by its de-excitation into the ground state of the ion by the emission of X-rays and far ultraviolet photons.[58]
Bow shocks form as a result of the interaction between the solar wind and the cometary ionosphere, which is created by the ionization of gases in the coma. As the comet approaches the Sun, increasing outgassing rates cause the coma to expand, and the sunlight ionizes gases in the coma. When the solar wind passes through this ion coma, the bow shock appears.
The first observations were made in the 1980s and 1990s as several spacecraft flew by comets 21P/Giacobini–Zinner,[59] 1P/Halley,[60] and 26P/Grigg–Skjellerup.[61] It was then found that the bow shocks at comets are wider and more gradual than the sharp planetary bow shocks seen at, for example, Earth. These observations were all made near perihelion when the bow shocks already were fully developed.
The Rosetta spacecraft observed the bow shock at comet 67P/Churyumov–Gerasimenko at an early stage of bow shock development when the outgassing increased during the comet's journey toward the Sun. This young bow shock was called the "infant bow shock". The infant bow shock is asymmetric and, relative to the distance to the nucleus, wider than fully developed bow shocks.[62]
Typical direction of tails during a comet's orbit near the Sun
In the outer Solar System, comets remain frozen and inactive and are extremely difficult or impossible to detect from Earth due to their small size. Statistical detections of inactive comet nuclei in the Kuiper belt have been reported from observations by the Hubble Space Telescope[63][64] but these detections have been questioned.[65][66] As a comet approaches the inner Solar System, solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus, carrying dust away with them.
The streams of dust and gas each form their own distinct tail, pointing in slightly different directions. The tail of dust is left behind in the comet's orbit in such a manner that it often forms a curved tail called the type II or dust tail.[54] At the same time, the ion or type I tail, made of gases, always points directly away from the Sun because this gas is more strongly affected by the solar wind than is dust, following magnetic field lines rather than an orbital trajectory.[67] On occasions—such as when Earth passes through a comet's orbital plane, the antitail, pointing in the opposite direction to the ion and dust tails, may be seen.[68]
The observation of antitails contributed significantly to the discovery of solar wind.[69] The ion tail is formed as a result of the ionization by solar ultra-violet radiation of particles in the coma. Once the particles have been ionized, they attain a net positive electrical charge, which in turn gives rise to an "induced magnetosphere" around the comet. The comet and its induced magnetic field form an obstacle to outward flowing solar wind particles. Because the relative orbital speed of the comet and the solar wind is supersonic, a bow shock is formed upstream of the comet in the flow direction of the solar wind. In this bow shock, large concentrations of cometary ions (called "pick-up ions") congregate and act to "load" the solar magnetic field with plasma, such that the field lines "drape" around the comet forming the ion tail.[70]
If the ion tail loading is sufficient, the magnetic field lines are squeezed together to the point where, at some distance along the ion tail, magnetic reconnection occurs. This leads to a "tail disconnection event".[70] This has been observed on a number of occasions, one notable event being recorded on 20 April 2007, when the ion tail of Encke's Comet was completely severed while the comet passed through a coronal mass ejection. This event was observed by the STEREO space probe.[71]
In 2013, ESA scientists reported that the ionosphere of the planet Venus streams outwards in a manner similar to the ion tail seen streaming from a comet under similar conditions."[72]
Uneven heating can cause newly generated gases to break out of a weak spot on the surface of comet's nucleus, like a geyser.[74] These streams of gas and dust can cause the nucleus to spin, and even split apart.[74] In 2010 it was revealed dry ice (frozen carbon dioxide) can power jets of material flowing out of a comet nucleus.[75] Infrared imaging of Hartley 2 shows such jets exiting and carrying with it dust grains into the coma.[76]
Most comets are small Solar System bodies with elongated elliptical orbits that take them close to the Sun for a part of their orbit and then out into the further reaches of the Solar System for the remainder.[77] Comets are often classified according to the length of their orbital periods: The longer the period the more elongated the ellipse.
Periodic comets or short-period comets are generally defined as those having orbital periods of less than 200 years.[78] They usually orbit more-or-less in the ecliptic plane in the same direction as the planets.[79] Their orbits typically take them out to the region of the outer planets (Jupiter and beyond) at aphelion; for example, the aphelion of Halley's Comet is a little beyond the orbit of Neptune. Comets whose aphelia are near a major planet's orbit are called its "family".[80] Such families are thought to arise from the planet capturing formerly long-period comets into shorter orbits.[81]
At the shorter orbital period extreme, Encke's Comet has an orbit that does not reach the orbit of Jupiter, and is known as an Encke-type comet. Short-period comets with orbital periods less than 20 years and low inclinations (up to 30 degrees) to the ecliptic are called traditional Jupiter-family comets (JFCs).[82][83] Those like Halley, with orbital periods of between 20 and 200 years and inclinations extending from zero to more than 90 degrees, are called Halley-type comets (HTCs).[84][85] As of 2022, 94 HTCs have been observed,[86] compared with 744 identified JFCs.[87]
Recently discovered main-belt comets form a distinct class, orbiting in more circular orbits within the asteroid belt.[88]
Because their elliptical orbits frequently take them close to the giant planets, comets are subject to further gravitational perturbations.[89] Short-period comets have a tendency for their aphelia to coincide with a giant planet's semi-major axis, with the JFCs being the largest group.[83] It is clear that comets coming in from the Oort cloud often have their orbits strongly influenced by the gravity of giant planets as a result of a close encounter. Jupiter is the source of the greatest perturbations, being more than twice as massive as all the other planets combined. These perturbations can deflect long-period comets into shorter orbital periods.[90][91]
Based on their orbital characteristics, short-period comets are thought to originate from the centaurs and the Kuiper belt/scattered disc[92] —a disk of objects in the trans-Neptunian region—whereas the source of long-period comets is thought to be the far more distant spherical Oort cloud (after the Dutch astronomer Jan Hendrik Oort who hypothesized its existence).[93] Vast swarms of comet-like bodies are thought to orbit the Sun in these distant regions in roughly circular orbits. Occasionally the gravitational influence of the outer planets (in the case of Kuiper belt objects) or nearby stars (in the case of Oort cloud objects) may throw one of these bodies into an elliptical orbit that takes it inwards toward the Sun to form a visible comet. Unlike the return of periodic comets, whose orbits have been established by previous observations, the appearance of new comets by this mechanism is unpredictable.[94] When flung into the orbit of the sun, and being continuously dragged towards it, tons of matter are stripped from the comets which greatly influence their lifetime; the more stripped, the shorter they live and vice versa.[95]
Long-period comets have highly eccentric orbits and periods ranging from 200 years to thousands or even millions of years.[96] An eccentricity greater than 1 when near perihelion does not necessarily mean that a comet will leave the Solar System.[97] For example, Comet McNaught had a heliocentric osculating eccentricity of 1.000019 near its perihelion passage epoch in January 2007 but is bound to the Sun with roughly a 92,600-year orbit because the eccentricity drops below 1 as it moves farther from the Sun. The future orbit of a long-period comet is properly obtained when the osculating orbit is computed at an epoch after leaving the planetary region and is calculated with respect to the center of mass of the Solar System. By definition long-period comets remain gravitationally bound to the Sun; those comets that are ejected from the Solar System due to close passes by major planets are no longer properly considered as having "periods". The orbits of long-period comets take them far beyond the outer planets at aphelia, and the plane of their orbits need not lie near the ecliptic. Long-period comets such as C/1999 F1 and C/2017 T2 (PANSTARRS) can have aphelion distances of nearly 70,000 AU (0.34 pc; 1.1 ly) with orbital periods estimated around 6 million years.
Single-apparition or non-periodic comets are similar to long-period comets because they also have parabolic or slightly hyperbolic trajectories[96] when near perihelion in the inner Solar System. However, gravitational perturbations from giant planets cause their orbits to change. Single-apparition comets have a hyperbolic or parabolic osculating orbit which allows them to permanently exit the Solar System after a single pass of the Sun.[98] The Sun's Hill sphere has an unstable maximum boundary of 230,000 AU (1.1 pc; 3.6 ly).[99] Only a few hundred comets have been seen to reach a hyperbolic orbit (e > 1) when near perihelion[100] that using a heliocentric unperturbed two-body best-fit suggests they may escape the Solar System.
As of 2019, only two objects have been discovered with an eccentricity significantly greater than one: 1I/ʻOumuamua and 2I/Borisov, indicating an origin outside the Solar System. While ʻOumuamua, with an eccentricity of about 1.2, showed no optical signs of cometary activity during its passage through the inner Solar System in October 2017, changes to its trajectory—which suggests outgassing—indicate that it is probably a comet.[101] On the other hand, 2I/Borisov, with an estimated eccentricity of about 3.36, has been observed to have the coma feature of comets, and is considered the first detected interstellar comet.[102][103] Comet C/1980 E1 had an orbital period of roughly 7.1 million years before the 1982 perihelion passage, but a 1980 encounter with Jupiter accelerated the comet giving it the largest eccentricity (1.057) of any known solar comet with a reasonable observation arc.[104] Comets not expected to return to the inner Solar System include C/1980 E1, C/2000 U5, C/2001 Q4 (NEAT), C/2009 R1, C/1956 R1, and C/2007 F1 (LONEOS).
Some authorities use the term "periodic comet" to refer to any comet with a periodic orbit (that is, all short-period comets plus all long-period comets),[105] whereas others use it to mean exclusively short-period comets.[96] Similarly, although the literal meaning of "non-periodic comet" is the same as "single-apparition comet", some use it to mean all comets that are not "periodic" in the second sense (that is, to also include all comets with a period greater than 200 years).
Early observations have revealed a few genuinely hyperbolic (i.e. non-periodic) trajectories, but no more than could be accounted for by perturbations from Jupiter. Comets from interstellar space are moving with velocities of the same order as the relative velocities of stars near the Sun (a few tens of km per second). When such objects enter the Solar System, they have a positive specific orbital energy resulting in a positive velocity at infinity ({\displaystyle v_{\infty }\!}{\displaystyle v_{\infty }\!}) and have notably hyperbolic trajectories. A rough calculation shows that there might be four hyperbolic comets per century within Jupiter's orbit, give or take one and perhaps two orders of magnitude.[106]
The Oort cloud is thought to occupy a vast space starting from between 2,000 and 5,000 AU (0.03 and 0.08 ly)[108] to as far as 50,000 AU (0.79 ly)[84] from the Sun. This cloud encases the celestial bodies that start at the middle of our solar system—the sun, all the way to outer limits of the Kuiper Belt. The Oort cloud consists of viable materials necessary for the creation of celestial bodies. The planets we have today, exist only because of the planetesimals (chunks of leftover space that assisted in the creation of planets) that were condensed and formed by the gravity of the sun. The eccentric made from these trapped planetesimals is why the Oort Cloud even exists.[109] Some estimates place the outer edge at between 100,000 and 200,000 AU (1.58 and 3.16 ly).[108] The region can be subdivided into a spherical outer Oort cloud of 20,000–50,000 AU (0.32–0.79 ly), and a doughnut-shaped inner cloud, the Hills cloud, of 2,000–20,000 AU (0.03–0.32 ly).[110] The outer cloud is only weakly bound to the Sun and supplies the long-period (and possibly Halley-type) comets that fall to inside the orbit of Neptune.[84] The inner Oort cloud is also known as the Hills cloud, named after J. G. Hills, who proposed its existence in 1981.[111] Models predict that the inner cloud should have tens or hundreds of times as many cometary nuclei as the outer halo;[111][112][113] it is seen as a possible source of new comets that resupply the relatively tenuous outer cloud as the latter's numbers are gradually depleted. The Hills cloud explains the continued existence of the Oort cloud after billions of years.[114]
Exocomets beyond the Solar System have also been detected and may be common in the Milky Way.[115] The first exocomet system detected was around Beta Pictoris, a very young A-type main-sequence star, in 1987.[116][117] A total of 11 such exocomet systems have been identified as of 2013, using the absorption spectrum caused by the large clouds of gas emitted by comets when passing close to their star.[115][116] For ten years the Kepler space telescope was responsible for searching for planets and other forms outside of the solar system. The first transiting exocomets were found in February 2018 by a group consisting of professional astronomers and citizen scientists in light curves recorded by the Kepler Space Telescope.[118][119] After Kepler Space Telescope retired in October 2018, a new telescope called TESS Telescope has taken over Kepler's mission. Since the launch of TESS, astronomers have discovered the transits of comets around the star Beta Pictoris using a light curve from TESS.[120][121] Since TESS has taken over, astronomers have since been able to better distinguish exocomets with the spectroscopic method. New planets are detected by the white light curve method which is viewed as a symmetrical dip in the charts readings when a planet overshadows its parent star. However, after further evaluation of these light curves, it has been discovered that the asymmetrical patterns of the dips presented are caused by the tail of a comet or of hundreds of comets.[122]
...he Sun, outgassing of its icy components also releases solid debris too large to be swept away by radiation pressure and the solar wind.[123] If Earth's orbit sends it through that trail of debris, which is composed mostly of fine grains of rocky material, there is likely to be a meteor shower as Earth passes through. Denser trails of debris produce quick but intense meteor showers and less dense trails create longer but less intense showers. Typically, the density of the debris trail is related to how long ago the parent comet released the material.[124][125] The Perseid meteor shower, for example, occurs every year between 9 and 13 August, when Earth passes through the orbit of Comet Swift–Tuttle. Halley's Comet is the source of the Orionid shower in October.[126][127]
Many comets and asteroids collided with Earth in its early stages. Many scientists think that comets bombarding the young Earth about 4 billion years ago brought the vast quantities of water that now fill Earth's oceans, or at least a significant portion of it. Others have cast doubt on this idea.[128] The detection of organic molecules, including polycyclic aromatic hydrocarbons,[18] in significant quantities in comets has led to speculation that comets or meteorites may have brought the precursors of life—or even life itself—to Earth.[129] In 2013 it was suggested that impacts between rocky and icy surfaces, such as comets, had the potential to create the amino acids that make up proteins through shock synthesis.[130] The speed at which the comets entered the atmosphere, combined with the magnitude of energy created after initial contact, allowed smaller molecules to condense into the larger macro-molecules that served as the foundation for life.[131] In 2015, scientists found significant amounts of molecular oxygen in the outgassings of comet 67P, suggesting that the molecule may occur more often than had been thought, and thus less an indicator of life as has been supposed.[132]
It is suspected that comet impacts have, over long timescales, also delivered significant quantities of water to Earth's Moon, some of which may have survived as lunar ice.[133] Comet and meteoroid impacts are also thought to be responsible for the existence of tektites and australites.[134]
Fear of comets as acts of God and signs of impending doom was highest in Europe from AD 1200 to 1650.[135] The year after the Great Comet of 1618, for example, Gotthard Arthusius published a pamphlet stating that it was a sign that the Day of Judgment was near.[136] He listed ten pages of comet-related disasters, including "earthquakes, floods, changes in river courses, hail storms, hot and dry weather, poor harvests, epidemics, war and treason and high prices".[135]
By 1700 most scholars concluded that such events occurred whether a comet was seen or not. Using Edmond Halley's records of comet sightings, however, William Whiston in 1711 wrote that the Great Comet of 1680 had a periodicity of 574 years and was responsible for the worldwide flood in the Book of Genesis, by pouring water on Earth. His announcement revived for another century fear of comets, now as direct threats to the world instead of signs of disasters.[135] Spectroscopic analysis in 1910 found the toxic gas cyanogen in the tail of Halley's Comet,[137] causing panicked buying of gas masks and quack "anti-comet pills" and "anti-comet umbrellas" by the public.[138]
If a comet is traveling fast enough, it may leave the Solar System. Such comets follow the open path of a hyperbola, and as such, they are called hyperbolic comets. Solar comets are only known to be ejected by interacting with another object in the Solar System, such as Jupiter.[139] An example of this is Comet C/1980 E1, which was shifted from an orbit of 7.1 million years around the Sun, to a hyperbolic trajectory, after a 1980 close pass by the planet Jupiter.[140] Interstellar comets such as 1I/ʻOumuamua and 2I/Borisov never orbited the Sun and therefore do not require a 3rd-body interaction to be ejected from the Solar System.
Jupiter-family comets and long-period comets appear to follow very different fading laws. The JFCs are active over a lifetime of about 10,000 years or ~1,000 orbits whereas long-period comets fade much faster. Only 10% of the long-period comets survive more than 50 passages to small perihelion and only 1% of them survive more than 2,000 passages.[32] Eventually most of the volatile material contained in a comet nucleus evaporates, and the comet becomes a small, dark, inert lump of rock or rubble that can resemble an asteroid.[141] Some asteroids in elliptical orbits are now identified as extinct comets.[142][143][144][145] Roughly six percent of the near-Earth asteroids are thought to be extinct comet nuclei.[32]
The nucleus of some comets may be fragile, a conclusion supported by the observation of comets splitting apart.[146] A significant cometary disruption was that of Comet Shoemaker–Levy 9, which was discovered in 1993. A close encounter in July 1992 had broken it into pieces, and over a period of six days in July 1994, these pieces fell into Jupiter's atmosphere—the first time astronomers had observed a collision between two objects in the Solar System.[147][148] Other splitting comets include 3D/Biela in 1846 and 73P/Schwassmann–Wachmann from 1995 to 2006.[149] Greek historian Ephorus reported that a comet split apart as far back as the winter of 372–373 BC.[150] Comets are suspected of splitting due to thermal stress, internal gas pressure, or impact.[151]
Comets 42P/Neujmin and 53P/Van Biesbroeck appear to be fragments of a parent comet. Numerical integrations have shown that both comets had a rather close approach to Jupiter in January 1850, and that, before 1850, the two orbits were nearly identical.[152]
Some comets have been observed to break up during their perihelion passage, including great comets West and Ikeya–Seki. Biela's Comet was one significant example when it broke into two pieces during its passage through the perihelion in 1846. These two comets were seen separately in 1852, but never again afterward. Instead, spectacular meteor showers were seen in 1872 and 1885 when the comet should have been visible. A minor meteor shower, the Andromedids, occurs annually in November, and it is caused when Earth crosses the orbit of Biela's Comet.[153]
Some comets meet a more spectacular end – either falling into the Sun[154] or smashing into a planet or other body. Collisions between comets and planets or moons were common in the early Solar System: some of the many craters on the Moon, for example, may have been caused by comets. A recent collision of a comet with a planet occurred in July 1994 when Comet Shoemaker–Levy 9 broke up into pieces and collided with Jupiter.[155]
The names given to comets have followed several different conventions over the past two centuries. Prior to the early 20th century, most comets were simply referred to by the year when they appeared, sometimes with additional adjectives for particularly bright comets; thus, the "Great Comet of 1680", the "Great Comet of 1882", and the "Great January Comet of 1910".
After Edmond Halley demonstrated that the comets of 1531, 1607, and 1682 were the same body and successfully predicted its return in 1759 by calculating its orbit, that comet became known as Halley's Comet.[157] Similarly, the second and third known periodic comets, Encke's Comet[158] and Biela's Comet,[159] were named after the astronomers who calculated their orbits rather than their original discoverers. Later, periodic comets were usually named after their discoverers, but comets that had appeared only once continued to be referred to by the year of their appearance.[160]
In the early 20th century, the convention of naming comets after their discoverers became common, and this remains so today. A comet can be named after its discoverers or an instrument or program that helped to find it.[160] For example, in 2019, astronomer Gennady Borisov observed a comet that appeared to have originated outside of the solar system; the comet was named C/2019 Q4 (Borisov) after him.
From ancient sources, such as Chinese oracle bones, it is known that comets have been noticed by humans for millennia.[161] Until the sixteenth century, comets were usually considered bad omens of deaths of kings or noble men, or coming catastrophes, or even interpreted as attacks by heavenly beings against terrestrial inhabitants.[162][163]
Aristotle (384–322 BC) was the first known scientist to utilize various theories and observational facts to employ a consistent, structured cosmological theory of comets. He believed that comets were atmospheric phenomena, due to the fact that they could appear outside of the zodiac and vary in brightness over the course of a few days. Aristotle's cometary theory arose from his observations and cosmological theory that everything in the cosmos is arranged in a distinct configuration.[164] Part of this configuration was a clear separation between the celestial and terrestrial, believing comets to be strictly associated with the latter. According to Aristotle, comets must be within the sphere of the moon and clearly separated from the heavens. Also in the 4th century BC, Apollonius of Myndus supported the idea that comets moved like the planets.[165] Aristotelian theory on comets continued to be widely accepted throughout the Middle Ages, despite several discoveries from various individuals challenging aspects of it.[166]
In the 1st century AD, Seneca the Younger questioned Aristotle's logic concerning comets. Because of their regular movement and imperviousness to wind, they cannot be atmospheric,[167] and are more permanent than suggested by their brief flashes across the sky.[a] He pointed out that only the tails are transparent and thus cloudlike, and argued that there is no reason to confine their orbits to the zodiac.[167] In criticizing Apollonius of Myndus, Seneca argues, "A comet cuts through the upper regions of the universe and then finally becomes visible when it reaches the lowest point of its orbit."[168] While Seneca did not author a substantial theory of his own,[169] his arguments would spark much debate among Aristotle's critics in the 16th and 17th centuries.[166][b]
Also in the 1st century, Pliny the Elder believed that comets were connected with political unrest and death.[171] Pliny observed comets as "human like", often describing their tails with "long hair" or "long beard".[172] His system for classifying comets according to their color and shape was used for centuries.[173]
In India, by the 6th century astronomers believed that comets were celestial bodies that re-appeared periodically. This was the view expressed in the 6th century by the astronomers Varāhamihira and Bhadrabahu, and the 10th-century astronomer Bhaṭṭotpala listed the names and estimated periods of certain comets, but it is not known how these figures were calculated or how accurate they were.[174]
According to Norse mythology, comets were actually a part of the Giant Ymir's skull. According to the tale, Odin and his brothers slew Ymir and set about constructing the world (Earth) from his corpse. They fashioned the oceans from his blood, the soil from his skin and muscles, vegetation from his hair, clouds from his brains, and the sky from his skull. Four dwarves, corresponding to the four cardinal points, held Ymir's skull aloft above the earth. Following this tale, comets in the sky, as believed by the Norse, were flakes of Ymir's skull falling from the sky and then disintegrating.[176]
In 1301, the Italian painter Giotto was the first person to accurately and anatomically portray a comet. In his work Adoration of the Magi, Giotto's depiction of Halley's Comet in the place of the Star of Bethlehem would go unmatched in accuracy until the 19th century and be bested only with the invention of photography.[175]
Astrological interpretations of comets proceeded to take precedence clear into the 15th century, despite the presence of modern scientific astronomy beginning to take root. Comets continued to forewarn of disaster, as seen in the Luzerner Schilling chronicles and in the warnings of Pope Callixtus III.[175] In 1578, German Lutheran bishop Andreas Celichius defined comets as "the thick smoke of human sins ... kindled by the hot and fiery anger of the Supreme Heavenly Judge". The next year, Andreas Dudith stated that "If comets were caused by the sins of mortals, they would never be absent from the sky."[177]
Scientific approach
Crude attempts at a parallax measurement of Halley's Comet were made in 1456, but were erroneous.[178] Regiomontanus was the first to attempt to calculate diurnal parallax by observing the great comet of 1472. His predictions were not very accurate, but they were conducted in the hopes of estimating the distance of a comet from the Earth.[173]
In the 16th century, Tycho Brahe and Michael Maestlin demonstrated that comets must exist outside of Earth's atmosphere by measuring the parallax of the Great Comet of 1577.[179] Within the precision of the measurements, this implied the comet must be at least four times more distant than from Earth to the Moon.[180][181] Based on observations in 1664, Giovanni Borelli recorded the longitudes and latitudes of comets that he observed, and suggested that cometary orbits may be parabolic.[182] Galileo Galilei, one of the most renowned astronomers to date, even attempted writings on comets in The Assayer. He rejected Brahe's theories on the parallax of comets and claimed that they may be a mere optical illusion. Intrigued as early scientists were about the nature of comets, Galileo could not help but throw about his own theories despite little personal observation.[173] Maestlin's student Johannes Kepler responded to these unjust criticisms in his work Hyperaspistes. Jakob Bernoulli published another attempt to explain comets (Conamen Novi Systematis Cometarum) in 1682.
Also occurring in the early modern period was the study of comets and their astrological significance in medical disciplines. Many healers of this time considered medicine and astronomy to be inter-disciplinary and employed their knowledge of comets and other astrological signs for diagnosing and treating patients.[183]
Isaac Newton, in his Principia Mathematica of 1687, proved that an object moving under the influence of gravity by an inverse square law must trace out an orbit shaped like one of the conic sections, and he demonstrated how to fit a comet's path through the sky to a parabolic orbit, using the comet of 1680 as an example.[184] He describes comets as compact and durable solid bodies moving in oblique orbit and their tails as thin streams of vapor emitted by their nuclei, ignited or heated by the Sun. He suspected that comets were the origin of the life-supporting component of air.[185] He also pointed out that comets usually appear near the Sun, and therefore most likely orbit it.[167] On their luminosity, he stated, "The comets shine by the Sun's light, which they reflect," with their tails illuminated by "the Sun's light reflected by a smoke arising from [the coma]".[167]
In 1705, Edmond Halley (1656–1742) applied Newton's method to 23 cometary apparitions that had occurred between 1337 and 1698. He noted that three of these, the comets of 1531, 1607, and 1682, had very similar orbital elements, and he was further able to account for the slight differences in their orbits in terms of gravitational perturbation caused by Jupiter and Saturn. Confident that these three apparitions had been three appearances of the same comet, he predicted that it would appear again in 1758–9.[186] Halley's predicted return date was later refined by a team of three French mathematicians: Alexis Clairaut, Joseph Lalande, and Nicole-Reine Lepaute, who predicted the date of the comet's 1759 perihelion to within one month's accuracy.[187][188] When the comet returned as predicted, it became known as Halley's Comet.[189]
As early as the 18th century, some scientists had made correct hypotheses as to comets' physical composition. In 1755, Immanuel Kant hypothesized in his Universal Natural History that comets were condensed from "primitive matter" beyond the known planets, which is "feebly moved" by gravity, then orbit at arbitrary inclinations, and are partially vaporized by the Sun's heat as they near perihelion.[191] In 1836, the German mathematician Friedrich Wilhelm Bessel, after observing streams of vapor during the appearance of Halley's Comet in 1835, proposed that the jet forces of evaporating material could be great enough to significantly alter a comet's orbit, and he argued that the non-gravitational movements of Encke's Comet resulted from this phenomenon.[192]
In the 19th century, the Astronomical Observatory of Padova was an epicenter in the observational study of comets. Led by Giovanni Santini (1787–1877) and followed by Giuseppe Lorenzoni (1843–1914), this observatory was devoted to classical astronomy, mainly to the new comets and planets orbit calculation, with the goal of compiling a catalog of almost ten thousand stars. Situated in the Northern portion of Italy, observations from this observatory were key in establishing important geodetic, geographic, and astronomical calculations, such as the difference of longitude between Milan and Padua as well as Padua to Fiume.[193] In addition to these geographic observations, correspondence within the observatory, particularly between Santini and another astronomer Giuseppe Toaldo, about the importance of comet and planetary orbital observations.[194]
In 1950, Fred Lawrence Whipple proposed that rather than being rocky objects containing some ice, comets were icy objects containing some dust and rock.[195] This "dirty snowball" model soon became accepted and appeared to be supported by the observations of an armada of spacecraft (including the European Space Agency's Giotto probe and the Soviet Union's Vega 1 and Vega 2) that flew through the coma of Halley's Comet in 1986, photographed the nucleus, and observed jets of evaporating material.[196]
On 22 January 2014, ESA scientists reported the detection, for the first definitive time, of water vapor on the dwarf planet Ceres, the largest object in the asteroid belt.[197] The detection was made by using the far-infrared abilities of the Herschel Space Observatory.[198] The finding is unexpected because comets, not asteroids, are typically considered to "sprout jets and plumes". According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids."[198] On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution of HCN, HNC, H2CO, and dust inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON).[199][200]
Debate continues about how much ice is in a comet. In 2001, the Deep Space 1 spacecraft obtained high-resolution images of the surface of Comet Borrelly. It was found that the surface of comet Borrelly is hot and dry, with a temperature of between 26 to 71 °C (79 to 160 °F), and extremely dark, suggesting that the ice has been removed by solar heating and maturation, or is hidden by the soot-like material that covers Borrelly. In July 2005, the Deep Impact probe blasted a crater on Comet Tempel 1 to study its interior. The mission yielded results suggesting that the majority of a comet's water ice is below the surface and that these reservoirs feed the jets of vaporized water that form the coma of Tempel 1. Renamed EPOXI, it made a flyby of Comet Hartley 2 on 4 November 2010.
In 2007, the Ulysses probe unexpectedly passed through the tail of the comet C/2006 P1 (McNaught) which was discovered in 2006. Ulysses was launched in 1990 and the intended mission was for Ulysses to orbit around the sun for further study at all latitudes.
Data from the Stardust mission show that materials retrieved from the tail of Wild 2 were crystalline and could only have been "born in fire", at extremely high temperatures of over 1,000 °C (1,830 °F). Although comets formed in the outer Solar System, radial mixing of material during the early formation of the Solar System is thought to have redistributed material throughout the proto-planetary disk. As a result, comets also contain crystalline grains that formed in the early, hot inner Solar System. This is seen in comet spectra as well as in sample return missions. More recent still, the materials retrieved demonstrate that the "comet dust resembles asteroid materials". These new results have forced scientists to rethink the nature of comets and their distinction from asteroids.
The Rosetta probe orbited Comet Churyumov–Gerasimenko. On 12 November 2014, its lander Philae successfully landed on the comet's surface, the first time a spacecraft has ever landed on such an object.
Approximately once a decade, a comet becomes bright enough to be noticed by a casual observer, leading such comets to be designated as great comets. Predicting whether a comet will become a great comet is notoriously difficult, as many factors may cause a comet's brightness to depart drastically from predictions. Broadly speaking, if a comet has a large and active nucleus, will pass close to the Sun, and is not obscured by the Sun as seen from Earth when at its brightest, it has a chance of becoming a great comet. However, Comet Kohoutek in 1973 fulfilled all the criteria and was expected to become spectacular but failed to do so.[210] Comet West, which appeared three years later, had much lower expectations but became an extremely impressive comet.
The Great Comet of 1577 is a well-known example of a great comet. It passed near Earth as a non-periodic comet and was seen by many, including well-known astronomers Tycho Brahe and Taqi ad-Din. Observations of this comet led to several significant findings regarding cometary science, especially for Brahe.
The late 20th century saw a lengthy gap without the appearance of any great comets, followed by the arrival of two in quick succession—Comet Hyakutake in 1996, followed by Hale–Bopp, which reached maximum brightness in 1997 having been discovered two years earlier. The first great comet of the 21st century was C/2006 P1 (McNaught), which became visible to naked eye observers in January 2007. It was the brightest in over 40 years.
A sun-grazing comet is a comet that passes extremely close to the Sun at perihelion, generally within a few million kilometers. Although small sungrazers can be completely evaporated during such a close approach to the Sun, larger sungrazers can survive many perihelion passages. However, the strong tidal forces they experience often lead to their fragmentation.
About 90% of the sungrazers observed with SOHO are members of the Kreutz group, which all originate from one giant comet that broke up into many smaller comets during its first passage through the inner Solar System. The remainder contains some sporadic sungrazers, but four other related groups of comets have been identified among them: the Kracht, Kracht 2a, Marsden, and Meyer groups. The Marsden and Kracht groups both appear to be related to Comet 96P/Machholz, which is also the parent of two meteor streams, the Quadrantids and the Arietids.
Of the thousands of known comets, some exhibit unusual properties. Comet Encke (2P/Encke) orbits from outside the asteroid belt to just inside the orbit of the planet Mercury whereas the Comet 29P/Schwassmann–Wachmann currently travels in a nearly circular orbit entirely between the orbits of Jupiter and Saturn. 2060 Chiron, whose unstable orbit is between Saturn and Uranus, was originally classified as an asteroid until a faint coma was noticed. Similarly, Comet Shoemaker–Levy 2 was originally designated asteroid 1990 UL3.
The largest known periodic comet is 95P/Chiron at 200 km in diameter that comes to perihelion every 50 years just inside of Saturn's orbit at 8 AU. The largest known Oort cloud comet is suspected of being Comet Bernardinelli-Bernstein at ≈150 km that will not come to perihelion until January 2031 just outside of Saturn's orbit at 11 AU. The Comet of 1729 is estimated to have been ≈100 km in diameter and came to perihelion inside of Jupiter's orbit at 4 AU.
Centaurs typically behave with characteristics of both asteroids and comets.[220] Centaurs can be classified as comets such as 60558 Echeclus, and 166P/NEAT. 166P/NEAT was discovered while it exhibited a coma, and so is classified as a comet despite its orbit, and 60558 Echeclus was discovered without a coma but later became active, and was then classified as both a comet and an asteroid (174P/Echeclus). One plan for Cassini involved sending it to a centaur, but NASA decided to destroy it instead.
A comet may be discovered photographically using a wide-field telescope or visually with binoculars. However, even without access to optical equipment, it is still possible for the amateur astronomer to discover a sun-grazing comet online by downloading images accumulated by some satellite observatories such as SOHO. SOHO's 2000th comet was discovered by Polish amateur astronomer Michał Kusiak on 26 December 2010 and both discoverers of Hale–Bopp used amateur equipment (although Hale was not an amateur).
A number of periodic comets discovered in earlier decades or previous centuries are now lost comets. Their orbits were never known well enough to predict future appearances or the comets have disintegrated. However, occasionally a "new" comet is discovered, and calculation of its orbit shows it to be an old "lost" comet. An example is Comet 11P/Tempel–Swift–LINEAR, discovered in 1869 but unobservable after 1908 because of perturbations by Jupiter. It was not found again until accidentally rediscovered by LINEAR in 2001. There are at least 18 comets that fit this category.
The depiction of comets in popular culture is firmly rooted in the long Western tradition of seeing comets as harbingers of doom and as omens of world-altering change. Halley's Comet alone has caused a slew of sensationalist publications of all sorts at each of its reappearances. It was especially noted that the birth and death of some notable persons coincided with separate appearances of the comet, such as with writers Mark Twain (who correctly speculated that he'd "go out with the comet" in 1910) and Eudora Welty, to whose life Mary Chapin Carpenter dedicated the song "Halley Came to Jackson".
In times past, bright comets often inspired panic and hysteria in the general population, being thought of as bad omens. More recently, during the passage of Halley's Comet in 1910, Earth passed through the comet's tail, and erroneous newspaper reports inspired a fear that cyanogen in the tail might poison millions, whereas the appearance of Comet Hale–Bopp in 1997 triggered the mass suicide of the Heaven's Gate cult.
The Lagoon Nebula
Messier 8 or NGC 6523 is a giant interstellar cloud in the constellation Sagittarius.
It is classified as an emission nebula and as an H II region.
The Lagoon Nebula was discovered by Guillaume Le Gentil in 1747 and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes.
Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core.
Taken with a 8" newt on a EQ5
20x1min @ ISO 400
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Photographed at Algonquin Provincial Park, Ontario, Canada
* Temperature 13 degrees C.
* Altitude of the nebula while I was photographing it: 19 degrees
This large glowing cloud of red hydrogen gas - famous among amateur astronomers - is faintly visible to the unaided eye, and rides very low in the summer sky as seen from the northern hemisphere.
Just to the left of centre is NGC 6530, a bright very young (~2 million years) open cluster of stars that were likely formed from the gases of the nebula itself.
Total exposure time: 8 minutes
For a wide-angle view of this object with the nearby Trifid Nebula, from June 20, click here:
www.flickr.com/photos/97587627@N06/18883919019/
From Wikipedia:
"The Lagoon Nebula (catalogued as Messier 8, and as NGC 6523) is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as a H II region.
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000 & 6,000 light years from the Earth. In the sky of Earth, it spans 90' by 40', translates to an actual dimension of 110 by 50 light years. Like many nebulae, it appears pink in time-exposure colour photos but is grey to the eye peering through binoculars or a telescope, human vision having poor colour sensitivity at low light levels. The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel) .... In 2006 the first four Herbig–Haro objects were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it."
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Nikon D810a camera body on Explore Scientific 152 mm (6 inch) refracting telescope
Mounted on Astrophysics 1100GTO equatorial mount
Eight stacked frames; each frame:
ISO 4000; 1-minute exposure at f/8, unguided
(with LENR - long exposure noise reduction)
Stacked in RegiStar;
Processed in Photoshop CS6 (brightness, contrast, levels, sharpening)
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Scanned lith print.
Rollei Vintage 332 RC (?) found in a black plastic bag (who knows how long it has been in there?) and lith printed.
Very unfamiliar process results and outcome for this, so I may be questioning if that's the paper noted on the bag or not (or has it just gotten old?).
A very quick establishment of the print contours already after <30 sec, and then almost nothing happend... On some of the prints there's this wavy cloudlike pattern all over, not bad IMO (but it was not there on the negative).
Jan 8, 2022. Rolleiflex T w/ Tessar 75 mm/3.5 + yellow filter.
Fomapan 100 dev in Rodinal 1+100, semistand 1 h.
Lith printed on Rollei vintage 332 RC and developed in Moersch Easy Lith (25A+25B+H2Oqs750ml).
Toned in Se 1+9, 45 sec.
Conclusion: The Rollei Vintage 332 RC has been aging during the years so it's not a very good lith paper anymore.
I have no idea what it was initially... I later found out it was a Noctilucent cloud
There are three luminous objects in this photo. The Orange glow is Twilight and green glow is the Aurora and the Last is the Noctilucent cloud that formed in between the two.
Noctilucent clouds, also known as polar mesospheric clouds, are bright cloudlike atmospheric phenomena visible in a deep twilight. The name means roughly "night shining" in Latin. They are most commonly observed in the summer months at latitudes between 50° and 70° north and south of the equator.
Scanned lith print.
Rollei Vintage 332 RC (?) found in a black plastic bag, cut down to 8x8" (who knows how long it has been in there?) and lith printed.
Very unfamiliar process results and outcome for this, so I may be questioning if that's the paper noted on the bag or not (or has it just gotten old?).
A very quick establishment of the print contours already after <30 sec, and then almost nothing happend... On some of the prints there's this wavy cloudlike pattern all over, not bad IMO (but it was not there on the negative).
Jan 8, 2022. Rolleiflex T w/ Tessar 75 mm/3.5 + yellow filter.
Fomapan 100 dev in Rodinal 1+100, semistand 1 h.
Lith printed on Rollei vintage 332 RC and developed in Moersch Easy Lith (25A+25B+H2Oqs750ml).
Toned in Se 1+9, 45 sec.
Conclusion: The Rollei Vintage 332 RC har been aging during the years so it's not a very good lith paper anymore.
Skoghall, Värmland.
The Lagoon Nebula (also known as Messier Object 8 (M8) and NGC 6523) is a giant interstellar cloud, classified as an emission nebula and H II region, in the constellation Sagittarius. At an estimated distance of 4,100 light-years, the Lagoon is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. In binoculars, the Lagoon is a distinct oval cloudlike patch with a definite core, like a pale celestial flower. The nebula has a fragile star cluster superimposed on it, making this one of the leading celestial sights of summer night skies.
LRGB + Ha light frames - stack of total time 250 mins
Telescope: Skywatcher ED80
CCD: ATIK 314L Mono
Location: Gytheio Lakonias, Greece
Drifting through a sea of Cow Parsley. Whispers in the breeze.
"Cow Parsley is a hollow-stemmed, tall plant that grows rapidly in the summer before dying back. It likes shady habitats in particular, and can be found decorating woodland edges, roadside verges and hedgerows with masses of frothy, white flowers. These flower umbels (umbrella-like clusters) appear from May until June.
The large, flat umbrellas of small white flowers, and large, fern-like leaves are familiar characteristics of Cow Parsley. When crushed between the fingers, the leaves produce a strong, almost aniseed-like scent. One of several common members of the carrot family, this is the most abundant, and the earliest-flowering of the roadside umbellifers, collectively referred to as 'Queen Anne's Lace"". www.wildlifetrusts.org/species/cow-parsley
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Photographed 4.5 km north of (13 km by road from) Uluru-Kata Tjuta National Park (Ayers Rock), Northern Territory, Australia, between 22.00 and 22.15 CAST (Central Australia Standard Time)
* Observing site: Long. 131.07° E. | Lat. 25.22° S. | Elev. 501 m
* Altitude of centre of nebula at time of exposures: ~55°
* Total exposure time: 14 minutes
* 660 mm focal length telescope
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Description:
One of the most prominent, largest, brightest and well known nebulae in the sky is the Lagoon Nebula, which is a favourite target of amateur astronomers with modest telescopes.
From Wikipedia: "The Lagoon Nebula ... is a giant interstellar cloud ... classified as an emission nebula and as an H II region. [It] was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. Within the nebula is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years away from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. ... The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296."
For a version of this photo WITHOUT LABELS, click on your screen to the LEFT of the photo, or click here:
www.flickr.com/photos/97587627@N06/49280286667
Here is a photo of the gear that used for astrophotography on this trip:
www.flickr.com/photos/97587627@N06/49017804808
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Technical information:
Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic astrograph, mounted on iOptron CEM40 equatorial mount
Fourteen stacked subframes - each frame:
ISO 5000; 1 minute exposure at f/5.2, 660 mm focal length, unguided
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (brightness, contrast, levels, colour balance)
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