... Credit: Roth Ritter ( Dark Atmospheres ) Explanation: Galactic or open star clusters are relatively young. ... This bright open cluster, known as M46 , is around 300 million years young and still contains a few hundred stars within its span of 30 light-years or so. ... In the lovely starscape , the colorful, circular patch just below the center of M46 (also inset at upper left) is the planetary nebula NGC 2438. ... Publications with keywords: open cluster - planetary nebula - M46 . ...