by Ann » Mon Aug 01, 2016 6:36 am
Comet PanSTARRS. Photo: José J. Chambó.
I think this image of Comet PanSTARRS is absolutely lovely, not least because of the beautiful colors, as seen when the path of green comet seems to have crossed a blue and a yellow star. The blue star is HD 129685, spectral class A0V, mag. 4.9, B-V ≈ 0.02, distance ≈ 215 light-years, luminosity ≈ 39 solar. The yellow star is HD 129456, spectral class K3III, mag. ≈ 4.1, B-V ≈ 1.4, distance ≈ 210 light-years, luminosity ≈ 81 solar. The stars are at very similar distances, and their colors, spectral classes and luminosities suggest they might be related, because A-type main sequence stars get brighter when they evolve into K-type giants. But in fact these stars are probably not related at all, because they have extremely different proper motions. The yellow star could possibly be a (slow)
halo star, somewhat similar to (but fainter than) Arcturus.
The blue star at bottom right is a so called Ap Si star, a silicon-enhanced peculiar star classified as an A-type star, even though it is as hot and as bright as a B-type star. Its B-V is ≈ −0.08, and its luminosity is ≈ 160 times solar.
In any case, this is a very lovely image with splendid colors!
Ann
[float=left][img2]http://www.spektrum.de/fm/1027/thumbnails/2013X1_160725_2400.jpg.2183062.jpg[/img2][c][size=75]Comet PanSTARRS. Photo: José J. Chambó.[/size][/c][/float] I think this image of Comet PanSTARRS is absolutely lovely, not least because of the beautiful colors, as seen when the path of green comet seems to have crossed a blue and a yellow star. The blue star is HD 129685, spectral class A0V, mag. 4.9, B-V ≈ 0.02, distance ≈ 215 light-years, luminosity ≈ 39 solar. The yellow star is HD 129456, spectral class K3III, mag. ≈ 4.1, B-V ≈ 1.4, distance ≈ 210 light-years, luminosity ≈ 81 solar. The stars are at very similar distances, and their colors, spectral classes and luminosities suggest they might be related, because A-type main sequence stars get brighter when they evolve into K-type giants. But in fact these stars are probably not related at all, because they have extremely different proper motions. The yellow star could possibly be a (slow) [url=https://en.wikipedia.org/wiki/Stellar_kinematics#Halo_stars]halo star[/url], somewhat similar to (but fainter than) Arcturus.
The blue star at bottom right is a so called Ap Si star, a silicon-enhanced peculiar star classified as an A-type star, even though it is as hot and as bright as a B-type star. Its B-V is ≈ −0.08, and its luminosity is ≈ 160 times solar.
In any case, this is a very lovely image with splendid colors! :D
Ann