NGC 7771 Galaxy Group (2009 August 29)

[Vivian]

http://apod.nasa.gov/apod/ap090829.html

http://antwrp.gsfc.nasa.gov/apod/image/ ... 1biggs.jpg

It seems that there is a strange red light spot on NGC 7771. Why?

Vivian

[geckzilla]

Foreground star? Looks like it got caught by whatever post-processing was done to colorize the galaxies which makes it look like it's part of the galaxy. Kind of deceiving. I wonder how Kent went about colorizing them.

[Chris Peterson]

http://antwrp.gsfc.nasa.gov/apod/image/ ... 1biggs.jpg

It seems that there is a strange red light spot on NGC 7771. Why?

This is a common processing artifact seen in astroimages. If you look closely, you'll see that it is actually a white spot surrounded by an orange ring. There are others in the image as well, all on top of galaxies. These are stars, and the reason they look that way is because the areas of nebulosity have been selectively boosted in brightness- taking along any overlapping stars. The boost is enough to saturate the stars themselves (which is why they show a white, blown-out core), and to drive up the wings of the stars enough that we see colored rings around them.