The Crescent Nebula, visible in the center of the image, was created by the brightest star in its center. One hypothesis has the Crescent Nebula beginning form about 250,000 years ago. At that time, the massive central star had evolved and began shedding its outer envelope in a strong stellar wind, ejecting the equivalent of our Sun's mass every 10,000 years. This wind impacted surrounding gas left over from a previous phase, compacting it into a series of complex shells, and lighting it up. The Crescent Nebula, also known as NGC 6888, lies about 4,700 light-years away in the constellation of Cygnus.