by Ann » Wed Apr 03, 2013 4:32 pm
Thanks for commenting on this image, saturno2! I agree, it's a nice image. It is always fun when two "cosmic objects" that are wildly different in size appears to be similar, because of their vastly different distances from us. I suppose that if we know how big these two objects are intrinsically, then we can figure out how much farther away Andromeda is than PANSTARRS!
As always, I find the colors of the objects interesting. Andromeda, as it happens, is a quite red galaxy. Its U-B index is +0.50, and its B-V index is +0.92. That's red. Judging from its U-B and B-V indexes alone, M31 could have been a "red and dead" galaxy, without any star formation at all. It's a good thing, then, that Andromeda is so nearby, so that we can see all its young stars and emission nebulae - although no pink gas clouds can be seen in this particular image, and the large association of young stars, NGC 206, can just barely be spotted in the lower left part of the galaxy.
We may note, however, that the overall color of Comet PANSTARRS is
almost the same as the overall color of Andromeda. Andromeda, admittedly, is just a tad yellower due to its bright yellow bulge. PANSTARRS is the same white color "all over", reflecting the Sun's B-V of 0.656 ± 0.005. For whatever reason, PANSTARRS apparently lacks both the typical green comet coma and a blue ion tail.
Ann
Thanks for commenting on this image, saturno2! I agree, it's a nice image. It is always fun when two "cosmic objects" that are wildly different in size appears to be similar, because of their vastly different distances from us. I suppose that if we know how big these two objects are intrinsically, then we can figure out how much farther away Andromeda is than PANSTARRS! 8-)
As always, I find the colors of the objects interesting. Andromeda, as it happens, is a quite red galaxy. Its U-B index is +0.50, and its B-V index is +0.92. That's red. Judging from its U-B and B-V indexes alone, M31 could have been a "red and dead" galaxy, without any star formation at all. It's a good thing, then, that Andromeda is so nearby, so that we can see all its young stars and emission nebulae - although no pink gas clouds can be seen in this particular image, and the large association of young stars, NGC 206, can just barely be spotted in the lower left part of the galaxy.
We may note, however, that the overall color of Comet PANSTARRS is [i]almost[/i] the same as the overall color of Andromeda. Andromeda, admittedly, is just a tad yellower due to its bright yellow bulge. PANSTARRS is the same white color "all over", reflecting the Sun's B-V of 0.656 ± 0.005. For whatever reason, PANSTARRS apparently lacks both the typical green comet coma and a blue ion tail.
Ann