by Ann » Fri Nov 07, 2014 2:02 am
As I leafed through James D Wray's
The Color Atlas of Galaxies, I came across this beautiful specimen of a lenticular galaxy,
NGC 4026. The discription in the link calls NGC 4026 an edge-on spiral galaxy, but that's not what it is. In James D Wray's closeup of the galaxy, taken with the McDonald 2.1 meter telescope, we can see that there is no dust in the galaxy and no structure at all, apart from the very prominent disk. James D. Wray wrote:
This is the type example of an S0 galaxy (disk, no evident dust and no recent star formation.)
As I checked up NGC 4026, I found that it was small, smaller indeed than NGC 4762. Yes, but it is noticeably redder than NGC 4762. It is farther away and therefore likely more affected by intergalactic dust, but on the other hand it is located in the direction of Ursa Major, where there is comparatively little dust between ourselves and other galaxies.
The only lenticular galaxy I could find that is comparative in color to NGC 4762 is
NGC 205, the larger but fainter of the Andromeda galaxy's two obvious satellite galaxies. The B-V colors of NGC 205 and NGC 4762 are similar, but the U-B color of NGC 205 is noticeably bluer than the U-B color of NGC 4762. And indeed, Adam Block's image of NGC 205 shows the existence of not only two small dust clouds in Andromeda's satellite galaxy, but also the presence of a small bluish population near the center of this galaxy. So it could be that NGC 205 should not actually be classified as an S0 galaxy, since it does contain dust and even some moderately recent star formation.
I think I stand corrected when I said that small galaxies aren't very red. That can't be true, since I found some quite red and quite small S0 galaxies. But at least I was correct when I said that NGC 4762 is indeed a very white S0-type galaxy.
Ann
As I leafed through James D Wray's [i]The Color Atlas of Galaxies[/i], I came across this beautiful specimen of a lenticular galaxy, [url=http://astrim.free.fr/NGC4026.htm]NGC 4026[/url]. The discription in the link calls NGC 4026 an edge-on spiral galaxy, but that's not what it is. In James D Wray's closeup of the galaxy, taken with the McDonald 2.1 meter telescope, we can see that there is no dust in the galaxy and no structure at all, apart from the very prominent disk. James D. Wray wrote:
[quote]This is the type example of an S0 galaxy (disk, no evident dust and no recent star formation.)[/quote]
As I checked up NGC 4026, I found that it was small, smaller indeed than NGC 4762. Yes, but it is noticeably redder than NGC 4762. It is farther away and therefore likely more affected by intergalactic dust, but on the other hand it is located in the direction of Ursa Major, where there is comparatively little dust between ourselves and other galaxies.
The only lenticular galaxy I could find that is comparative in color to NGC 4762 is [url=http://www.noao.edu/outreach/aop/observers/n205.html]NGC 205[/url], the larger but fainter of the Andromeda galaxy's two obvious satellite galaxies. The B-V colors of NGC 205 and NGC 4762 are similar, but the U-B color of NGC 205 is noticeably bluer than the U-B color of NGC 4762. And indeed, Adam Block's image of NGC 205 shows the existence of not only two small dust clouds in Andromeda's satellite galaxy, but also the presence of a small bluish population near the center of this galaxy. So it could be that NGC 205 should not actually be classified as an S0 galaxy, since it does contain dust and even some moderately recent star formation.
I think I stand corrected when I said that small galaxies aren't very red. That can't be true, since I found some quite red and quite small S0 galaxies. But at least I was correct when I said that NGC 4762 is indeed a very white S0-type galaxy.
Ann