APOD: Blue Comet PanSTARRS (2018 Jan 12)

[APOD Robot]

Blue Comet PanSTARRS

Explanation: Discovered with the PanSTARRS telescope on September 7, 2016, this Comet PanSTARRS, C/2016 R2, is presently about 24 light minutes (3 AU) from the Sun, sweeping through planet Earth's skies across the background of stars in the constellation Taurus. An inbound visitor from our Solar System's distant Oort Cloud, its beautiful and complex ion tail is a remarkable shade of blue. Still relatively far from the Sun, the comet's already well-developed ion tail is very impressive. Emission from unusually abundant ionized carbon monoxide (CO+) atoms fluorescing in the increasing sunlight is largely responsible for the pretty blue tint. This color image of the blue comet is a combination of data taken from two different telescopes during the night of January 7. Located at the apex of the V-shaped Hyades star cluster in Taurus, bright star Gamma Tauri is responsible for the glow at the bottom left corner of the frame.

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[dave67r]

I'm curious as to why it appears that there is a date of 2018-01-18 12:40 UTC in the top left corner of this image? Or am I misreading what's there?

THX

[geckzilla]

I'm curious as to why it appears that there is a date of 2018-01-18 12:40 UTC in the top left corner of this image? Or am I misreading what's there?

THX

I think you're right. You can see a black and white version he posted that has the correct date. One wonders how it got switched.
https://twitter.com/peachastro

[bystander]

I'm curious as to why it appears that there is a date of 2018-01-18 12:40 UTC in the top left corner of this image? Or am I misreading what's there?

THX

Obviously this image hasn't been taken yet, but at least we know it's coming.

On Jose J. Chambo's page it states the image was taken on 07 Jan 2018. Maybe the date-time was off in the camera.

[Ann]

I would love to be able to identify the other stars in this image, to be able to judge the color of the comet.

The bright star whose glow can be seen in the lower left corner is gamma Taurus. What about the other stars? Is north up and east to the left in this image?

Thanks for the picture, Damian Peach and Jose J. Chambo!

Ann

[EricDevis]

When looking at http://spaceweathergallery.com/indiv_up ... _id=141786 I notice some other moving objects. One bright dot goes "slowly" from left to right, apparently through the comet's tail. What are they? Other comets? Stars? What are they?

[PepeChambo]

Obviously this image hasn't been taken yet, but at least we know it's coming.
On Jose J. Chambo's page it states the image was taken on 07 Jan 2018. Maybe the date-time was off in the camera.

Obviously the image has already been taken, a little mistake at labeling

I would love to be able to identify the other stars in this image, to be able to judge the color of the comet.
The bright star whose glow can be seen in the lower left corner is gamma Taurus. What about the other stars? Is north up and east to the left in this image?
Thanks for the picture, Damian Peach and Jose J. Chambo!
Ann

North is up and West to right. Thanks Ann.

[Ann]

I would love to be able to identify the other stars in this image, to be able to judge the color of the comet.
The bright star whose glow can be seen in the lower left corner is gamma Taurus. What about the other stars? Is north up and east to the left in this image?
Thanks for the picture, Damian Peach and Jose J. Chambo!
Ann

North is up and West to right. Thanks Ann.

Thanks! But I still can't get my bearings, unfortunately.

What is that bright white-looking star near the "head" of the comet?

Ann

[Case]

get my bearings

Astrometry.net can process this image and help identify its place in the sky. The bright star is identified as HD 27029.

[Ann]

get my bearings

Astrometry.net can process this image and help identify its place in the sky. The bright star is identified as HD 27029.

Thanks, that's really interesting!

The B-V index of HD 27029 is +1.1, which makes it a marginally redder star than Pollux (+0.99). I believe that the blue-looking star at top center is HD 27029, whose B-V index is +0.7, marginally bluer than Capella but slightly redder than the Sun.

This suggests to me that the comet may not be all that blue after all, since it doesn't look much bluer than stars that are redder than the Sun.

Ann

[orin stepanek]

Cool: what a neat Photo!

[Dr. Work]

CO is a molecule, so there are no such things as CO atoms.

[Chris Peterson]

The B-V index of HD 27029 is +1.1, which makes it a marginally redder star than Pollux (+0.99). I believe that the blue-looking star at top center is HD 27029, whose B-V index is +0.7, marginally bluer than Capella but slightly redder than the Sun.

This suggests to me that the comet may not be all that blue after all, since it doesn't look much bluer than stars that are redder than the Sun.

The comet is certainly blue, since we know what the source of the emission is and what wavelength it produces.

Keep in mind that color indexes are not reliable for judging the apparent color of anything other than thermal sources, and you can't reliably compare the colors of thermal sources and emission sources in most images due to the nature of the filters used to derive color information.

[Ann]

The B-V index of HD 27029 is +1.1, which makes it a marginally redder star than Pollux (+0.99). I believe that the blue-looking star at top center is HD 27029, whose B-V index is +0.7, marginally bluer than Capella but slightly redder than the Sun.

This suggests to me that the comet may not be all that blue after all, since it doesn't look much bluer than stars that are redder than the Sun.

The comet is certainly blue, since we know what the source of the emission is and what wavelength it produces.

Keep in mind that color indexes are not reliable for judging the apparent color of anything other than thermal sources, and you can't reliably compare the colors of thermal sources and emission sources in most images due to the nature of the filters used to derive color information.

Point taken (although you may not agree with me there).

I have never come across a star with a B-V index of +0.7 or larger that looked the least bit blue through a telescope. Yet the stars look blue here.

Perhaps the stars and the comet were photographed through different filters, or maybe the picture was processed in such a way that the stars look bluer than they would to the eye, while the color of the comet was processed differently?

Ann

[Chris Peterson]

The B-V index of HD 27029 is +1.1, which makes it a marginally redder star than Pollux (+0.99). I believe that the blue-looking star at top center is HD 27029, whose B-V index is +0.7, marginally bluer than Capella but slightly redder than the Sun.

This suggests to me that the comet may not be all that blue after all, since it doesn't look much bluer than stars that are redder than the Sun.

The comet is certainly blue, since we know what the source of the emission is and what wavelength it produces.

Keep in mind that color indexes are not reliable for judging the apparent color of anything other than thermal sources, and you can't reliably compare the colors of thermal sources and emission sources in most images due to the nature of the filters used to derive color information.

Point taken (although you may not agree with me there).

I have never come across a star with a B-V index of +0.7 or larger that looked the least bit blue through a telescope. Yet the stars look blue here.

Perhaps the stars and the comet were photographed through different filters, or maybe the picture was processed in such a way that the stars look bluer than they would to the eye, while the color of the comet was processed differently?

Of course, through a telescope the comet will only look gray.

I've never seen any stars that look particularly blue. The most intense color I've seen leans towards pale orange. All star colors are very low saturation to the eye. But they almost always show a pretty high degree of saturation in images... a consequence of how the intensity is flattened.

[De58te]

Utterly FANTASTIC! Today's APOD picture was photographed 6 days in the future! Or is that, will be photographed 6 days in the future? This must mean somebody out there has invented a working time machine. Far out!

[Ann]

I've never seen any stars that look particularly blue. The most intense color I've seen leans towards pale orange. All star colors are very low saturation to the eye. But they almost always show a pretty high degree of saturation in images... a consequence of how the intensity is flattened.

I shouldn't keep arguing with you about this, since both of us are actually right. But I can't stop myself.

The most intensely colored stars are indeed the cool ones. There can be no doubt that Betelgeuse is a shade of yellow, maybe even yellow-orange, when seen through the telescope. And in fact, there really are stars whose color is a deep orange or even red. That color can be seen in some carbon stars like T Lyra, which looks very red here. A more realistic portrait of its color may be this one by Anthony Ayiomamitis.

Click to view full size image

Realistic colors in bright stars in Orion, Canis Major and Canis Minor.

Click to view full size image

[c]Blue-white Vega, Alpha Lyra. Inferior image source:
https://stargazerslounge.com/gallery/im ... tion-lyra/[/c]

And there really are stars that look blue too, or at least blue-white. The star that is most "famously blue" in the sky is probably Vega. Several people have attested to its blue-white hue. When I helped operate a telescope in the astronomy club that I'm no longer a member of, many visitors had a look at Vega through a 14 inch telescope, and they all agreed that it looked blue.

When I look at the stars without optical aid, Sirius is the only star that looks a bit blue to me.

Ann

[sillyworm2]

The ORT Cloud..How & Where did all this water/ice come to be/come from?

[Chris Peterson]

The ORT Cloud..How & Where did all this water/ice come to be/come from?

Hydrogen is the most abundant element in the Universe. In molecular clouds, oxygen is common, as well. H₂O is a simple molecule, easily formed. It would be surprising not to find lots of water in many places.

[sillyworm2]

Thanks Chris Now & I looked...where does the OXYGEN in "Space" come from?

[Chris Peterson]

Thanks Chris Now & I looked...where does the OXYGEN in "Space" come from?

Oxygen is a product of stellar nucleosynthesis. It is formed inside stars and released when the stars either blow off part of their atmospheres or explode in supernovas. One of the standard filters used for imaging both planetary nebulas and supernova remnants is one which isolates ionized oxygen, precisely because it is so abundant in those environments. In addition to free oxygen atoms and molecules, oxygen (being very reactive) forms many compounds, with silicates and carbonates both being major components of the dust left behind by exploding stars.

Of course, stars and planetary systems don't form in empty space, but in regions rich with gas and dust produced by previous generations of stars.

[sillyworm2]

Thanks AGAIN Chris! Please humor me...now..under what conditions does an OXYGEN rich atmosphere first form around a planet?

[rstevenson]

Thanks AGAIN Chris! Please humor me...now..under what conditions does an OXYGEN rich atmosphere first form around a planet?

Pond scum! All you need are warm shallow oceans full of cyanobacteria, aka blue-green algae. They give off oxygen as a by-product. Oh, and a few hundred million years to build up enough of the oxygen.

Nowadays, phytoplankton are doing a lot of that job, along with all the green plants in the world, but cyanobacteria got the whole thing started.

Rob

[Chris Peterson]

Thanks AGAIN Chris! Please humor me...now..under what conditions does an OXYGEN rich atmosphere first form around a planet?

Pond scum! All you need are warm shallow oceans full of cyanobacteria, aka blue-green algae. They give off oxygen as a by-product. Oh, and a few hundred million years to build up enough of the oxygen.

Nowadays, phytoplankton are doing a lot of that job, along with all the green plants in the world, but cyanobacteria got the whole thing started.

There also some ideas out there which consider non-biological mechanisms, but certainly, some sort of metabolic process like photosynthesis offers the best answer (and is the only one known by example to work).

FWIW, the organisms that get the ball rolling probably need to be suicidal. By raising the oxygen levels in the atmosphere, they effectively poison themselves. Oxygen is, of course, a potent biological poison which took organisms a long time to figure out how to use without killing themselves in the process.

[sillyworm2]

THANKS! Rob & Chris