by Ann » Tue Jan 22, 2013 6:12 am
Interesting. I don't have my software here as I am writing this, but my software isn't that good for checking up clusters anyway. I note that an unusual set of filters were used to produce this image: 336 nm (ultraviolet), mapped as blue, 475 nm (blue), mapped as green, and the old favorite 814 nm (infrared), mapped as red. It is quite unusual for HEIC to put so much effort into detecting blue and ultraviolet objects.
Anyway, it is clear from the visual appearance of the cluster that NGC 411 could not possibly be a globular cluster, at least not a typical very metal-poor globular. Such a globular cluster would have a rich population of blue horizontal branch stars, which are fainter than the red giants but clearly brighter than the main sequence stars. Here, there are a few bright blue stars that almost certainly don't belong to the cluster. There are, in fact, a few semi-bright blue stars too, but they are scattered far from the most star-rich part of the cluster in a most un-globular-cluster-like way. In the center there is a large population of faint mildly bluish main sequence stars and quite a lot of giant stars, which are all more or less orange in color.
Interesting.
Ann
Interesting. I don't have my software here as I am writing this, but my software isn't that good for checking up clusters anyway. I note that an unusual set of filters were used to produce this image: 336 nm (ultraviolet), mapped as blue, 475 nm (blue), mapped as green, and the old favorite 814 nm (infrared), mapped as red. It is quite unusual for HEIC to put so much effort into detecting blue and ultraviolet objects.
Anyway, it is clear from the visual appearance of the cluster that NGC 411 could not possibly be a globular cluster, at least not a typical very metal-poor globular. Such a globular cluster would have a rich population of blue horizontal branch stars, which are fainter than the red giants but clearly brighter than the main sequence stars. Here, there are a few bright blue stars that almost certainly don't belong to the cluster. There are, in fact, a few semi-bright blue stars too, but they are scattered far from the most star-rich part of the cluster in a most un-globular-cluster-like way. In the center there is a large population of faint mildly bluish main sequence stars and quite a lot of giant stars, which are all more or less orange in color.
Interesting.
Ann