APOD: 2012 January 7 - Grand Spiral Galaxy NGC 1232 (original) (raw)

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2012 January 7

Grand Spiral Galaxy NGC 1232
Image Credit: FORS,8.2-meter VLT Antu,ESO

Explanation: Galaxies are fascinating not only for what is visible, but for what is invisible.Grand spiral galaxyNGC 1232,captured in detail by one of the newVery Large Telescopes, is a good example. The visible is dominated by millions ofbright stars and darkdust, caught up in a gravitational swirl of spiral arms revolving about the center.Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanesof dense interstellardustcan be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts ofinterstellar gas, together wielding such high mass that they dominate the dynamics of the innergalaxy. Invisible are evengreater amounts of matter in a form we don't yet know - pervasivedark matter needed to explain themotionsof the visible in the outer galaxy.

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Authors & editors: Robert Nemiroff(MTU) &Jerry Bonnell (UMCP)
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