This picture of Messier 20 and 21 was made Astronomy Picture of the Day on August 28, 2014. Messier 20 and 21 refer to numbers 20 and 21 on a list of celestial objects noted by French astronomer Charles Messier. Messier 20, also known as the Trifid nebula, is a part of the zodiacal constellation Sagittarius. It is one of the youngest star-forming regions in our galaxy, being only 300,000 years old. Composed of stars, as well as gas clouds and natal dust, it forms a beautiful picture in the sky. Messier 21 is a relatively close open star cluster to the Trifid nebula.
