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Tuesday, March 21, 2017

Astronomy Picture of the Day

UGC 12591: The Fastest Rotating Galaxy Known 

Why does this galaxy spin so fast?

To start, even identifying which type of galaxy UGC 12591 is difficult -- it has dark dust lanes like a spiral galaxy but a large diffuse bulge of stars like a lenticular

Surprisingly observations show that UGC 12591 spins at about 480 km/sec, almost twice as fast as our Milky Way, and the fastest rotation rate yet measured.

The mass needed to hold together a galaxy spinning this fast is several times the mass of our Milky Way Galaxy.

Progenitor scenarios for UGC 12591 include slow growth by accreting ambient matter, or rapid growth through a recent galaxy collision or collisions -- future observations may tell.

The light we see today from UGC 12591 left about 400 million light years ago, when trees were first developing on Earth.

 See Explanation.  Clicking on the picture will download
 the highest resolution version available.

 Image Credit: NASAESAHubble