Globular star clusters harbor from a hundred thousand up to a million stars and roam the Milky Way halo. Like most globulars, M15 is filled with ancient stars, about 12 billion years old compared to the Sun's estimated 4.5 billion years. Its cool red giant stars appear yellowish in this color composite image. Unlike most globulars, M15 displays a planetary nebula , the briefly visible gaseous shroud of a dying star. Cataloged as Kuestner 648, M15's planetary nebula is the round pinkish cloud at the upper left.
Specific rights apply .