From a press release of the European Southern Observatory (ESO), September 23, 2015:
A new image of the rose-colored star forming region Messier 17 was captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It is one of the sharpest images showing the entire nebula and not only reveals its full size but also retains fine detail throughout the cosmic landscape of gas clouds, dust and newborn stars.
Although officially known as Messier 17, its nicknames include: the Omega Nebula, the Swan Nebula, the Checkmark Nebula, the Horseshoe Nebula and the Lobster Nebula. M17 is located about 5500 light-years from Earth near the plane of the Milky Way and in the constellation of Sagittarius. The object spans a big section of the sky — its gas and dust clouds measure about 15 light-years across. This material is fueling the birth of new stars and the wide field of view of the new picture reveals many stars in front of, in, or behind M17.
The nebula appears as a complex red structure with some graduation to pink. Its coloring is a signature of glowing hydrogen gas. The short-lived blue stars that recently formed in Messier 17 emit enough ultraviolet light to heat up surrounding gas to the extent that it begins to glow brightly. In the central region the colors are lighter, and some parts appear white. This white color is real — it arises as a result of mixing the light from the hottest gas with the starlight reflected by dust. Throughout this rosy glow, the nebula shows a web of darker regions of dust that obscure the light. This obscuring material is also glowing and — although these areas are dark in this visible-light image — they look bright when observed using infrared cameras.
Links: full ESO press release, including further images and movies of M17.