Distance: 5500 to 9000 light years
Image and Text by Robert Gendler
A gem of the summer sky, M20 allows us a view into the exciting science of star birth.
M20 is a young HII region (300,000 years old) about 30 light years across and is illuminated by the O-type supergiant HD 164492 at the center of its trilobed emission cloud. The ionizing star is about 30 times the mass of our sun and is the “A” component of a triple system ( A, B, and C components). In all there are seven members (HD 164492 A through G) of the small cluster packed within a half light year at the center of M20.
As an HII region M20 is similar to M42 in its complexity and relationship to its parent molecular cloud but is much younger. A large blue reflection cloud forms the northern border of M20 and is illuminated solely by the F-type supergiant HD 164514. Recent X-ray and infrared observations have discovered an amazing array of very early stars and protostars within M20 giving us a rare glimpse of the earliest stages of star birth.