Discovered by Giovanni Batista Hodierna before 1654.
M38 is an open cluster of stars that formed about 200 million years ago. It lies in the constellation of Auriga at a distance of approximately 4,200 light years. The cluster has a diameter of about 25 light years and, as viewed from Earth, is about two-thirds the size of the full Moon. The brightest star in the cluster is a 7.9 magnitude type GO yellow supergiant. Type G stars have a surface temperature of 5,000 to 6,000 degrees. In comparison to our own Sun, which is also a type G star, this supergiant star shines 900 times brighter.