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"Please dispose thoughtfully of your used postdocs"
via Bill Hooker @sennoma
80% of US postdocs never get a tenured position. see Bjoern Brembs
Lunar eclipses present an excellent opportunity to learn how to observe the atmospheres of those exoplanets in stellar systems that are appropriately and fortuitously oriented in space. The geometric configuration of the three bodies involved is similar when both produce a visible transit of a planet across the face of a star.
As seen from the Moon during a total lunar eclipse, the Earth passes in front of the Sun and almost completely shadows the face of the Moon from direct sunlight whilst it remains in umbral shadow. However, because the Earth has an atmosphere, some of the sunlight that grazes the limb is refracted and scattered towards the hidden Moon to paint it a deep, blood-red hue.
In regions free from cloud and high mountains, these grazing sunbeams will travel along a path containing up to about eighty times as much atmosphere as you would look through when observing a star at the zenith from sea level. This very long path, twice as long as a sunset or sunrise, imprints a strong signature of the atmospheric composition of the Earth on the light that reaches the Moon. By capturing this dim lunar light with a telescope and a spectrograph on or near the Earth we can interpret this signature to compile a detailed picture our own atmosphere.
While an exoplanet transit will not provide an umbral shadow that is accessible to us, it can place us in its penumbra. Teasing the signature of the exoplanet's atmosphere from a signal that is almost completely dominated by the unshadowed starlight requires a great deal of care and a large telescope. But it can, and has now quite often, been done. Although we do not yet have the telescopes to achieve this for exoplanets as small as Earth, several are now (2021) being constructed or planned.
This plot of the spectrum of a low Sun and two lunar eclipses is presented to show what the results look like and what they show.
Each of them reveal what is essentially the transmission of the Earth's atmosphere. This is calculated by taking the ratio of the transmitted light to the source which is, of course, the Sun. By taking this ratio, we remove all the spectral features arising at the Sun, leaving only those formed by the Earth's atmospheric absorption and scattering: we call these the 'telluric' lines and bands.
The top (blue line) spectrum is from the low Sun (altitude 8.4°) observed in Munich in August 2011. The visible part was obtained with a JAZ spectrometer while the infrared (from ~950nm) is from a NirQuest, both from Ocean Optics. In this case the ratio was taken with observations earlier in the day with a solar altitude of 51°.
The bottom (red line) spectrum, kindly supplied by Enric Pallé, is from the Moon in the Earth's umbral shadow taken from La Palma during the lunar eclipse of 16 August 2008. This was obtained by visible and infrared spectrographs on different telescopes. Full descriptions can be found in the Nature paper by Pallé et al. (Vol 459|11 June 2009|doi:10.1038/nature08050) along with supplementary information. See:
The central (green line) spectrum shows a low resolution representation of a considerably higher resolution spectrum extending up to 1000nm observed from China during the 10 December 2011 lunar eclipse. The detailed analysis of these observations is presented in the paper by Yan et al. (International Journal of Astrobiology 14 (2): 255–266, 2015). See:
Both of the eclipse spectra show the ratio of the measurements of the lunar surface during the umbral part of the eclipse to that of the same part of the bright Moon out of eclipse taken at closely adjacent times. This procedure removes not only the solar spectral features but also those resulting from the lunar surface itself and from the atmospheric path between the Moon and the telescope, leaving a clean measurement of the long grazing (tangential) path taken by the sunlight reaching the Moon past the Earth.
The infrared part of the spectrum, above 1000nm, is dominated by overtones of the fundamental water vapour bands associated with the stretching a bending of the water molecule (en.wikipedia.org/wiki/Electromagnetic_absorption_by_water). In addition to some carbon dioxide and methane absorptions, there are two important and interesting features associated with collisions between two oxygens and, in one case, between oxygen and nitrogen molecules. These are called Collision Induced Absorptions (CIA) which, because they require the close proximity of two molecules, have a strength which depends on the square of atmospheric density and so become especially strong when sunlight takes a path through the low atmosphere. In the plots, some of the stronger CIA bands are marked in pale green. The oxygen-oxygen collisions are labelled O_4. A modern quantum mechanical description of the formation of these bands can be found at: www.theochem.ru.nl/files/theses/karman-phdthesis-2018.pdf
Note the great strength of the O_4 + N_2•N_2 band in the umbral spectrum of the 2008 eclipse (red line) when almost all of the sunlight reaching the Moon has travelled though the low atmosphere.
The visible spectrum is marked by strong scattering (Rayleigh and aerosol) extinction and by very intense ozone (Chappuis band) absorption, the combination of which provides the colour palette of a lunar eclipse ranging from deep red-orange to ultramarine blue.
Of interest in the 2011 eclipse spectrum (green line) is the weakness of the water absorption spectrum. The tangent path of the sunlight reaching the Moon in this umbral spectrum passed over the coast of Antarctica south of Australia. Here the very low temperatures freeze out the water to give an extraordinarily dry atmosphere.
More details of the interpretations of the eclipse spectra can be found in the papers referred to above and also in an article entitled "How the Sun Paints the Sky" which can be found on the Herschel Society website at:
herschelsociety.org.uk/wp-content/uploads/2021/01/How-the...
I am turning into a bit of a nomad. This one only has two people in it (no fresh air freaks!). It has a window (although the same view as previously).
Book release (and lots of music) of a book about Goan writing in Portuguese. Authored by Dr (Fr)Eufemiano Miranda.
York University Lidar (Laser Radar) 1972 - Earliest prototype for NASA Phoenix Mission Lidar - This unit was designed and configured by the photographer as a PhD project during 1970-73 under the supervision of Professor Allan I. Carswell. This original Laser Radar (LIDAR) was used to probe the lower atmosphere above Toronto during and after atmospheric pollution episodes. The techniques for interpreting the data have become quite refined over the years. A miniaturized version of this device flew on the Mars Phoenix mission in 2009/10 and the LIDAR on board that craft successfully measured falling snow from the Martian surface. Photographer Russell McNeil PhD (Physics) lives in Nanaimo, British Columbia where he works also as a writer and a personal trainer.
I finally got around to sending my dissertation for bounding, almost a year after it was finished and signed.
A bit thin, ain't it? should have asked for some empty pages inserted in the middle. Nobody will ever actually look inside.
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses
I was updating my CV today and realised with a shock that it's 10 years since I got my PhD. Tempus has very much fugitted.
Scarier still is that I couldn't remember the title, despite agonising over it at the time (The application of HPLC-APCI MS to the regiospecific analysis of triacylglycerols in edible fats and oils, in case you're interested)(it's a riveting read!)(no, really it is, just avoid Chapter 7 because that was quite dodgy)(thankfully the external examiner needed to go to the pub at the end of Chapter 6).
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses
It's done! Four copies of my PhD thesis on my desk waiting to be bound and then to be submitted by tomorrow. Three years of work, finally done! :-)
Ofair's house, projected to be a cottage, express the maximun synthesis of Niemeyer's architectural concepts of this period.
Compare with the Errazuris house projected by Le Corbusier in 1930 in Cile.
All the images of this set are 3d reconstrucions of not realised houses