Starship Asterisk*

In reply to JXP; indeed the red and blue stars are cluster members. They're stars which have evolved off the main sequence, and thus become much brighter than main sequence stars of the same or lesser mass. For karlhein; that's a good question, and globular cluster formation is not well understood. ...

A couple points of interest: *The bright blue stars in the picture actually aren't blue stragglers, as implied by the caption; they're at a stage called the horizontal branch, in between two red giant stages. The HST press release for this image gets this small detail correct: http://hubblesite.org/...

This picture seemed really bizarre to me, with the assertion that Tethys is visible in the picture and casting the shadow to the far right. If Tethys is casting the shadow, it must be located on the line drawn from the shadow. If the visible moon is Tethys, its position "above" the rings (...