Messier

NASA

Astronomy Picture of the Day

A Messier Moment for Tempel 2 Explanation: Which of these is not a comet? You guessed it – the one on the right is a globular star cluster. The diffuse greenish coma of periodic comet 10P/Tempel 2 is at left in the frame. In fact the globular star cluster is Messier 30, also known as M30, or the 30th entry in astronomer Charles Messier’s catalog of…