Our Star
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…
Our Star
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…