November 27, 2008
You are a way for the cosmos to know itself, Carl Sagan once said. On your birthday, the cosmos got to know itself a little better.
Galaxies in the River
Birthday · November 27, 2008
A little universe, just for you
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APOD published November 27, 2008. Credit: Robert Gendler. A publication-date match, not a photo taken on your date. Independent of NASA.
Large galaxies grow by eating small ones. Even our own galaxy practices galactic cannibalism, absorbing small galaxies that get too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and well illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus (The River). Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531, a struggle the smaller galaxy will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. The NGC 1532/1531 pair is thought to be similar to the system of face-on spiral and small companion known as M51, the Whirlpool Galaxy.
Image credit: Robert Gendler