They think the halos are caused by galactic collisions. Very cool. Read the whole explanation at the link.
Since the shutdown effects NASA’s Astronomy picture website, I can’t pull a new image for this post. This is an older image I had saved in my “favorite pics” folder of the Aurora Borealis against a backdrop of stars. I still have dreams of making it to see the Northern Lights in person this year–2013 is a high year of solar activity before cycling back down.
Want to be name a nebula? NGC 7027 has been known since 1878 but still lacks a name. They’re taking suggestions.