by Ann » Thu Oct 23, 2014 7:56 am
Oh, that's a great picture! So glad to see it!
One thing that fascinates me about the Deer Lick Group (the scattered group of distant galaxies near large galaxy NGC 7331), when you compare it with the true members of Stephan's Quintet, is that all these galaxies are
more or less the same apparent size. Okay, the Deer Lick Group members look a bit bigger than the Sephan's Quintet ones, but not by much. This suggests to me that they are at relatively similar distances from us. And if we think of them like that, then we can really see how compact Stephan's Quintet is. The Deer Lick Group is probably a relatively "typical" galaxy group, unlike Stephan's Quintet, which is like a galactic train wreck. (Actually the Deer Lick group looks like a rather tight group too, and its members have probably had a lot of interaction, judging from the fact that there is little star formation here.)
I also like seeing the very blue color of NGC 7320, the foreground dwarf galaxy which is only masquerading as a member of Stephan's Quintet. Small starforming galaxies like NGC 7320 are typically quite blue. The reason is probably that they haven't built up a large population of old red and yellow stars, and moreover they have undergone so few episodes of star formation that they are still relatively metal-poor (that is, they contain low levels of elements heavier than hydrogen and helium). And metal-poor stars are typically bluer than metal-rich ones.
What a fine picture!
Ann
Oh, that's a great picture! So glad to see it! :D
One thing that fascinates me about the Deer Lick Group (the scattered group of distant galaxies near large galaxy NGC 7331), when you compare it with the true members of Stephan's Quintet, is that all these galaxies are [i]more or less[/i] the same apparent size. Okay, the Deer Lick Group members look a bit bigger than the Sephan's Quintet ones, but not by much. This suggests to me that they are at relatively similar distances from us. And if we think of them like that, then we can really see how compact Stephan's Quintet is. The Deer Lick Group is probably a relatively "typical" galaxy group, unlike Stephan's Quintet, which is like a galactic train wreck. (Actually the Deer Lick group looks like a rather tight group too, and its members have probably had a lot of interaction, judging from the fact that there is little star formation here.)
I also like seeing the very blue color of NGC 7320, the foreground dwarf galaxy which is only masquerading as a member of Stephan's Quintet. Small starforming galaxies like NGC 7320 are typically quite blue. The reason is probably that they haven't built up a large population of old red and yellow stars, and moreover they have undergone so few episodes of star formation that they are still relatively metal-poor (that is, they contain low levels of elements heavier than hydrogen and helium). And metal-poor stars are typically bluer than metal-rich ones.
What a fine picture!
Ann