M8 & M20

In the constellation of Sagittarius. Seven degrees north of the tip of the Archer's arrow (the star γ Sagittarii, “Al Nasl”), a very bright and beautiful region can be found: M8 (NGC 6523), the Lagoon Nebula. Discovered by Le Gentil in 1747, it sits in the galactic spiral arm immediately inside the one containing the Solar System; being seen in projection close to the core of the Milky Way, the area is marked by very diffuse brightness and a great abundance of stars. It lies about 4,100 light-years away and contains numerous star-forming regions, dark nebulae and Bok globules: one of the most interesting areas of the sky. About 8 degrees from the star “Al Nasl” we instead find M20, the Trifid Nebula, so named because its core is crossed by filaments of dark nebulosity that seem to split it into three parts. This nebula, too, lies about 5,000 light-years away, in the same galactic arm as the Lagoon Nebula. Its very bright central star, which illuminates much of the nebula, is estimated to be only 300,000 years old, making the Trifid one of the youngest known star-forming regions. The red colour comes from hydrogen, the light blue from oxygen, while the dark streaks are cold, unlit gas.