See Explanation. Clicking on the picture will download the highest resolution version available.
The Rosette Nebula is a large emission nebula located 3000 light-years away.

Source: NASA (public Domain) Credit: T. A. Rector, B. Wolpa, M. Hanna (AURA/NOAO/NSF)
http://antwrp.gsfc.nasa.gov/apod/ap000111.html