... In fact, 18th century cosmic tourist Charles Messier cataloged two of them; M8 , the large nebula left of center, and colorful M20 on the right. The third, NGC 6559 , is above M8, separated from the larger nebula by a dark dust lane. All three are stellar nurseries about five thousand light-years or so distant. ... Glowing hydrogen gas creates the dominant red color of the emission nebulae, with contrasting blue hues, most striking in the Trifid, due to dust reflected starlight. ...