APOD: Still Life with NGC 2170
Image Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona
Explanation: In this beautiful celestial still life composed with a cosmic brush, dusty nebula NGC 2170 shines at the upper left. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection nebulae, a compact red emission region, and streamers of obscuring dust against a backdrop of stars. Like the common household items still life painters often choose for their subjects, the clouds of gas, dust, and hot stars pictured here are also commonly found in this setting - a massive, star-forming molecular cloud in the constellation Monoceros. The giant molecular cloud, Mon R2, is impressively close, estimated to be only 2,400 light-years or so away. At that distance, this canvas would be about 15 light-years across.
Star Formation Region NGC 2170
Nebula NGC 2170 by Astrophotographer Russell Croman
This enigmatic region in the constellation of Monoceros displays a wonderful mix of nebula types. The bluish areas are reflection nebulas, so-named because they reflect the light of nearby stars. The dust particle size in these areas preferentially reflects blue light, similar to cigarette and other kinds of smoke. The red areas are emission nebulas, and shine by a different mechanism.
Ultraviolet light from nearby stars excites hydrogren and other gas atoms in the nebula, which then emit light of their own in specific colors. Finally, what looks a bit like black ink spilled across the image constitutes a dark nebula, and is only seen because of the light that it blocks. In other words, the dark nebula is seen in silhouette.
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