These three bright nebulae are often featured in telescopic toursof the constellation
Sagittarius and the view
toward the centerof our Milky Way galaxy.In fact, 18th century cosmic tourist
Charles Messiercataloged two of them; M8, the nebula above and left of center,and colorful M20 at the lower left.The third,
NGC 6559, is at the right of M8, separatedfrom the the larger nebula by a dark dust lane.All three are stellar nurseries aboutfive thousand light-years or so distant.The expansive M8, over a hundred light-years across,is also known as the
Lagoon Nebulawhile M20's popular moniker is
the Trifid.In this gorgeous
digital composition,the dominant red color of the emission nebulae is dueto glowing hydrogen gas energized by the radiation of hot,young stars.The contrasting blue hues, most striking in theTrifid as well as NGC 6559, are due to dust
reflected starlight .
Selected NASA's Astronomy Picture the Day for September 9, 2004.