M20, also known as the Trifid Nebula, is located in the constellation Sagittarius and lies approximately 5,000 light-years from the Earth. It was discovered by Charles Messier in 1773.  The nebula's common name of "Trifid" comes from its physical appearance of three segments defined by the prominent dark dust band that trisects the bright dust and gas of the nebula.  The dark dust feature of the Trifid has its own designation of Barnard 85.  The Trifid Nebula is visible in small telescopes and is a favorite object for amateur astronomers.  The nebula is an active stellar nursery.  Observations of the Spitzer Space Telescope have documented 30 embryonic stars and 120 newborn stars within the clouds of the nebula that are hidden from optical telescopes.
The image above is known as a mapped, or false, color image and was acquired using narrowband filters. It was assembled using the standard Hubble palette with SII mapped to Red, Ha mapped to Green and OIII mapped to Blue.