Orion: The Big Picture . ... Some of the stars that form the constellation of Orion are part of a giant gas cloud complex that stretches over 100 light years and appears more than 50 times the diameter of the Moon. Components of this cloud include the Horsehead Nebula , the Orion Nebula , the Trapezium open cluster , and small disks containing stellar systems which are just forming. At 1500 light years, Orion is the closest star forming region to Earth. ... NASA Official: Jay Norris. ...