APOD: Comet PanSTARRS with Galaxy (2014 Jun 06)

[APOD Robot]

Comet PanSTARRS with Galaxy

Explanation: Sweeping slowly through northern skies, the comet PanSTARRS C/2012 K1 posed for this telescopic portrait on June 2nd in the constellation Ursa Major. Now in the inner solar system, the icy body from the Oort cloud sports two tails, a lighter broad dust tail and crooked ion tail extending below and right. The comet's condensed greenish coma makes a nice contrast with the spiky yellowish background star above. NGC 3319 appears at the upper left of the frame that spans almost twice the apparent diameter of the full Moon. The spiral galaxy is about 47 million light-years away, far beyond the stars in our own Milky Way. In comparison, the comet was a mere 14 light-minutes from our fair planet. This comet PanSTARRS will slowly grow brighter in the coming months remaining a good target for telescopic comet watchers and reaching perihelion, its closest approach to the Sun, while just beyond Earth's orbit in late August.

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[Ann]

The appearance of galaxy NGC 3319 is most interesting. It appears to have a blue bar and three bright blue knots of intense star formation. This SDSS g-r-i image suggests that the star formation in the bar is real, and two of the three blue knots in an arm really seem to be pockets of star formation. The third blue knot appears to be a foreground star, however, and not even a blue one.

Ann

[Nitpicker]

The appearance of galaxy NGC 3319 is most interesting. It appears to have a blue bar and three bright blue knots of intense star formation. This SDSS g-r-i image suggests that the star formation in the bar is real, and two of the three blue knots in an arm really seem to be pockets of star formation. The third blue knot appears to be a foreground star, however, and not even a blue one.

Ann

And there's a comet in front, too. And little lambs eat ivy.

It is a great image. But it is perhaps a little silly to be comparing colours with another image, when the filter/exposure/processing details of neither are readily available.

[Ann]

The appearance of galaxy NGC 3319 is most interesting. It appears to have a blue bar and three bright blue knots of intense star formation. This SDSS g-r-i image suggests that the star formation in the bar is real, and two of the three blue knots in an arm really seem to be pockets of star formation. The third blue knot appears to be a foreground star, however, and not even a blue one.

Ann

And there's a comet in front, too. And little lambs eat ivy.

It is a great image. But it is perhaps a little silly to be comparing colours with another image, when the filter/exposure/processing details of neither are readily available.

I certainly realize that Alessandro Falesiedi didn't produce his very fine photo primarily in order to bring out the true colors of NGC 3319. Obviously this is a comet portrait more than anything else, or rather, it is a portrait of a comet seen against the sky.

There is absolutely no reason for Alessandro Falesiedi to make sure that his NGC 3319 colors are correct, but I wanted to check them against other pictures of NGC 3319. Again, not all galaxy pictures do a good job of bringing out the colors of the galaxy, but I generally trust SDSS. They use the same filters and often, though not always, the same processing and color balance. That is why I feel confident, judging from the SDSS picture, that the bar of NGC 3319 really is quite blue and really contains quite a lot of star formation. There are also two bright pockets of star formation in an arm, but a similarly bright point of light close to them is yellow in color and therefore not something that belongs to the galaxy. It is too bright to be a red giant in NGC 3319, so it is almost certainly a foreground star.

Compare the SDSS picture with this image by Adam Block. It shows a blue bar, two intense purple knots of star formation, and a yellow-orange stellar object that is most likely a foreground star.

By the way, the yellow star close to the comet in today's APOD is almost certainly HD 92388, a modest eighth magnitude K0 star.

Anyway, the main reason why I brought up the blue bar in NGC 3319 is that blue galactic bars are unusual. Galactic bars are generally old, stable features, made up of old yellow stars. The fact that the bar of NGC 3319 is bursting with young blue stars makes this galaxy unusual.

Ann

[Boomer12k]

Neat image....

:---[===] *

[Nitpicker]

Also seems like mirror images are the new black.

[BDanielMayfield]

This is a great APOD, with two facinating objects to discuss.

The comet's "crooked ion tail" is interesting. Ions are charged atoms, so the changes in its direction must be from magnetic effects.

Since the galaxy's bar is blue could it be a young galaxy, as galactic ages go?

Bruce

[starsurfer]

Adam Block needs to image NGC 3319!!

[LocalColor]

Oh my, this image was well composed and presented. Thank you.

Thanks for the info that this image was taken from the northern hemisphere. Looks like we might finally get some clear nights in our area for telescoping.

[Ann]

BDanielMayfield wrote:
Since the galaxy's bar is blue could it be a young galaxy, as galactic ages go?

That is an interesting question. I would guess that NGC 3319 definitely contains some very old stars.

http://en.wikipedia.org/wiki/I_Zwicky_18 wrote:
I Zwicky 18 is a dwarf irregular galaxy located about 59 million light years away.[2] The galaxy was first identified by Swiss astronomer Fritz Zwicky in a 1930s photographic survey of galaxies.[citation needed] Studies at the Palomar Observatory some 40 years ago led astronomers to believe that the galaxy erupted with star formation billions of years after its galactic neighbors. Galaxies resembling I Zwicky 18's youthful appearance are typically found only in the early universe. The Hubble Space Telescope, however, found faint, older stars contained within the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as ten billion years ago. The galaxy, therefore, may have formed at the same time as most other galaxies.

So dwarf galaxy I Zwicky 18 was believed to be a genuinely young galaxy whihc formed very recently, but as you can see from the Wikipedia entry, the Hubble Space Telescope revealed a population of old stars in this very young-looking galaxy. Therefore, I Zwicky 18 is no longer believed to be a very young galaxy, but rather it is thought to be an old galaxy that very recently erupted with intense star formation after, probably, billions of years of quiescence.

My guess is that NGC 3318 recently underwent some sort of "trauma" that caused it to form a great number of bars in its bar. Did it have a bar before? I would guess that it might have had an old, faint, yellow bar, which suddenly received a great inflow of gas and started forming young blue stars.

I own the book The Galaxies of the Local Group by Sidney van den Bergh. In this book, he argues that the bar of the Large Magellanic Cloud is younger than one billion years old, and that most of the stars in the LMC bar were born 4-200 million years ago. That suggests that there might have been a time when the bar of the LMC was as blue as the bar in NGC 3319 is today. Now the bar of the Large Magellanic is "middle-aged" and somewhat greenish.

But today most galactic bars are yellow. A few examples are M109, NGC 1300, NGC 1365, NGC 7427, NGC 2903 and many others. For more examples of galaxies with yellow bars, check out Adam Block's truly excellent galaxy page. Note two galaxies on that page with blue bars: NGC 1073 and NGC 7741. Check out this Hubble image of NGC 1073, which shows star formation in the bar of the galaxy.

Ann

[BMAONE23]

I wish I Z wicky 18 again
and going where I've never been
where ellipticals, like spirals
starting out just pretend
I wish I Z wicky 18 again

[astromazzo]

The tecnique to freeze both the comet and the stars is a distortion in the use of software: innaturally. To obtein more details on comet tail, is necessary to push layer (with Photoshop or others ...) of cyan and/or blue, so tail and dimm stars go that color - see Ligustri pictures here: (http://spaceweathergallery.com/indiv_up ... d_id=97101) and Damian Peach here: (http://spaceweather.com/images2014/02ju ... 22q499ltv7). I think this is not natural colors and also not pure RGB ... In an other layer the big stars are worked perfectly ... not are photographers but electronic painters! The really astrophotographs are these with a normal use of channels RGB or LRGB on the same image, that give the vision closer to the human, with high fidelity. I used a simple LRGB here: (http://asterisk.apod.com/download/file. ... &mode=view) or (http://spaceweathergallery.com/full_ima ... 702367.jpg) without complicated artifice of computer graphics. Easier is more true ...

[Chris Peterson]

The tecnique to freeze both the comet and the stars is a distortion in the use of software: innaturally. To obtein more details on comet tail, is necessary to push layer (with Photoshop or others ...) of cyan and/or blue, so tail and dimm stars go that color - see Ligustri pictures here: (http://spaceweathergallery.com/indiv_up ... d_id=97101) and Damian Peach here: (http://spaceweather.com/images2014/02ju ... 22q499ltv7). I think this is not natural colors and also not pure RGB ... In an other layer the big stars are worked perfectly ... not are photographers but electronic painters! The really astrophotographs are these with a normal use of channels RGB or LRGB on the same image, that give the vision closer to the human, with high fidelity. I used a simple LRGB here: (http://asterisk.apod.com/download/file. ... &mode=view) or (http://spaceweathergallery.com/full_ima ... 702367.jpg) without complicated artifice of computer graphics. Easier is more true ...

There are no "real" astroimages.

It's quite common with comets to isolate the comet from the background. It's certainly preferable when there's something more interesting than stars there.

[BDanielMayfield]

BDanielMayfield wrote:
Since the galaxy's bar is blue could it be a young galaxy, as galactic ages go?

That is an interesting question. I would guess that NGC 3319 definitely contains some very old stars.

http://en.wikipedia.org/wiki/I_Zwicky_18 wrote:
I Zwicky 18 is a dwarf irregular galaxy located about 59 million light years away.[2] The galaxy was first identified by Swiss astronomer Fritz Zwicky in a 1930s photographic survey of galaxies.[citation needed] Studies at the Palomar Observatory some 40 years ago led astronomers to believe that the galaxy erupted with star formation billions of years after its galactic neighbors. Galaxies resembling I Zwicky 18's youthful appearance are typically found only in the early universe. The Hubble Space Telescope, however, found faint, older stars contained within the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as ten billion years ago. The galaxy, therefore, may have formed at the same time as most other galaxies.

So dwarf galaxy I Zwicky 18 was believed to be a genuinely young galaxy whihc formed very recently, but as you can see from the Wikipedia entry, the Hubble Space Telescope revealed a population of old stars in this very young-looking galaxy. Therefore, I Zwicky 18 is no longer believed to be a very young galaxy, but rather it is thought to be an old galaxy that very recently erupted with intense star formation after, probably, billions of years of quiescence.

My guess is that NGC 3318 recently underwent some sort of "trauma" that caused it to form a great number of bars in its bar. Did it have a bar before? I would guess that it might have had an old, faint, yellow bar, which suddenly received a great inflow of gas and started forming young blue stars.

I own the book The Galaxies of the Local Group by Sidney van den Bergh. In this book, he argues that the bar of the Large Magellanic Cloud is younger than one billion years old, and that most of the stars in the LMC bar were born 4-200 million years ago. That suggests that there might have been a time when the bar of the LMC was as blue as the bar in NGC 3319 is today. Now the bar of the Large Magellanic is "middle-aged" and somewhat greenish.

But today most galactic bars are yellow. A few examples are M109, NGC 1300, NGC 1365, NGC 7427, NGC 2903 and many others. For more examples of galaxies with yellow bars, check out Adam Block's truly excellent galaxy page. Note two galaxies on that page with blue bars: NGC 1073 and NGC 7741. Check out this Hubble image of NGC 1073, which shows star formation in the bar of the galaxy.

Ann

Thanks Ann. So, our APOD co-star, the galaxy NGC 3319, is likely to be ordinary old, but it's sort of young at heart. Maybe it helps to have "a great number of bars in its bar."

[Ann]

My guess is that NGC 3318 recently underwent some sort of "trauma" that caused it to form a great number of bars in its bar.

OOOOPPSS!!!

Ha-ha!

Cheers!!

Ann

[Beyond]

Cheers. That was another bar located in a state of being with a cold... Mass a-a-a-a-choo sits. After you sneezes so hard, you goes and setts down.

[DavidLeodis]

The explanation states that the image was "posed" (taken) on June 2nd (2014 by implication). In the image's Exif information that I was able to find through the APOD image properties it however states that the image create date was "June 4, 2014 12:59:49AM (timezone is 2 hours ahead of GMT)" which will be June 3rd under GMT, so still not June 2nd. Assuming that the create date in Exif data should be the date an image was taken (unless obviously otherwise) then if the Exif data create date is wrong here then that seems to be a common problem, as I have queried Exif data dates before in some APODs (and have not bothered querying on many others).

[Chris Peterson]

The explanation states that the image was "posed" (taken) on June 2nd (2014 by implication). In the image's Exif information that I was able to find through the APOD image properties it however states that the image create date was "June 4, 2014 12:59:49AM (timezone is 2 hours ahead of GMT)" which will be June 3rd under GMT, so still not June 2nd. Assuming that the create date in Exif data should be the date an image was taken (unless obviously otherwise) then if the Exif data create date is wrong here then that seems to be a common problem, as I have queried Exif data dates before in some APODs (and have not bothered querying on many others). :?

The image was captured with a scientific camera that does not produce files containing EXIF headers. Everything in the header of the JPEG file that ultimately got published was either synthesized from information in the FITS headers of the three individual images (L, R, B) making up the source data, or added by the image processing software. In this case, I'd guess that the EXIF create date quite correctly reflects the date and time that the actual image was created from the camera data. Photoshop (or whatever) has no way of knowing when the data was collected.

[Astronymus]

The comet's "crooked ion tail" is interesting. Ions are charged atoms, so the changes in its direction must be from magnetic effects.

Or could it be caused by rotation and difference in chemical composition and resulting grades of ionisation?

[Chris Peterson]

The comet's "crooked ion tail" is interesting. Ions are charged atoms, so the changes in its direction must be from magnetic effects.

Or could it be caused by rotation and difference in chemical composition and resulting grades of ionisation?

The structure of a comet's ion tail is determined by electromagnetic interaction with the solar wind (primarily the magnetic component). The makeup of the gas tail (including the ion tail) is pretty uniform. Different parts of the tail are encountering solar wind with very different speeds, however.

[DavidLeodis]

Thank you Chris for your response to a post of mine a little earlier and also the others you have made to previous posts of mine in discussions on many APODs in regard to such as Exif uncertainties or astronomy questions. Your help is always appreciated, as it also is that you are prepared to take the effort to answer them.

It seems clear to me that I am about the only person that submits queries on differences between such as Exif data dates or errors in explanations (some of those could be picked up by using proof readers). I have therefore decided that as such things clearly do not bother most APOD viewers (if they ever spot them!) I shall no longer submit queries about them (unless otherwise). I shall still though continue to enjoy the daily APODs (well the vast majority of them!).

[Chris Peterson]

It seems clear to me that I am about the only person that submits queries on differences between such as Exif data dates or errors in explanations (some of those could be picked up by using proof readers). I have therefore decided that as such things clearly do not bother most APOD viewers (if they ever spot them!) I shall no longer submit queries about them (unless otherwise). I shall still though continue to enjoy the daily APODs (well the vast majority of them!).

Queries about the EXIF data in images and the catching of caption errors are both reasonable things to discuss. I wouldn't give up bringing these things up if they catch your eye.

[Astronymus]

The comet's "crooked ion tail" is interesting. Ions are charged atoms, so the changes in its direction must be from magnetic effects.

Or could it be caused by rotation and difference in chemical composition and resulting grades of ionisation?

The structure of a comet's ion tail is determined by electromagnetic interaction with the solar wind (primarily the magnetic component). The makeup of the gas tail (including the ion tail) is pretty uniform. Different parts of the tail are encountering solar wind with very different speeds, however.

Thanks for that explanation.

[ckooler]

A couple of the stars of the constellation Cassiopeia would serve as rough pointer stars to the great messier object and the comet, and scanning with my binoculars, I joyously found both low on the horizon.