NGC 772 with its small companion galaxy, NGC 770. Interactions with NGC 770
is likely what gives NGC 772 its strange shape. Image: Jim Thommes.
Today's APOD is a beautiful image. Please note the wealth of small background galaxies, which have been redshift-reddened to orange and reddish hues. It is likely that the reddest background galaxies are the most distant ones, but it is not quite certain, because a galaxy with an intrinsic old yellow population will look redder than a young starforming one at the same distance.
Note the yellow-white galaxy in the upper left corner, and the galaxy with the blue arms to the right of it. These two galaxies could be at the same distance, and they could be physically close to one another and interacting. They are more distant than NGC 772, but not so much so that their colors are strongly affected, given the filters that were used for this image (and the processing of the image). The largest yellow-white galaxy near bottom of the image could be at a comparable distance to the two at upper left.
Please note the blue star clusters that seem to be intermingled with the small red background galaxies, stretching all the way from left to right (or from right to left) in the lower part of the APOD. These blue clusters trace an outer arm of NGC 772.
NASA's now-defunct ultraviolet-detecting space telescope GALEX would have had a field day with NGC 772, making it look considerably larger at ultraviolet than at visible wavelengths due to the galaxy's ultraviolet-bright but visibly faint outer arm.
Take a look at galaxy NGC 1512 and its smaller companion NGC 1510 in visible and ultraviolet light to see what I mean by arms that suddenly pop into view at ultraviolet wavelengths:
Ann
Arp 78: Peculiar Galaxy in Aries
