This composite image of the strange spiral galaxy NGC 4921 was created using over 80 separate photos taken with yellow and near-infrared filters. In the background are several hundreds of more remote galaxies, collectively called the 'Coma Galaxy Cluster,' allogether stretching back into time to the early universe. The long exposure times of seventeen and te
n hours (respectively) employed by Hubble's Wide Field Camera used to capture the galaxy in all its brilliance is also responsible for the crisp, clear view of the distant galaxies located millions of light-years away.
Located roughly 320 million light-years away in the northern constellation of Coma Berenices, the Coma Galaxy Cluster is by far one of the most rich collections of galaxies in the not-so distant (so to speak) observable universe. None of which, is more spectacular than the one pictured here, NGC 4921.
Discovered back in in the late 18th century by the famed astronomer William Herchel, this galaxy gets its rare spiral shape due to the perpetual star formation processes that causes delicate swirls of gas and dust to form a ring around the whole galaxy, littered throughout are brilliant metal-poor blue stars that are destined to end their short lives in a brilliant explosion. The "barred" light in the galaxy's center is likely host to a supermassive black hole and the outer portion consists of poorly distinguished spiral arms, unlike those that are seen in typical spiral galaxies. One more interesting discovery, is that NGC 4921 is largely lacking in non-ionized hydrogen gas.
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