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Brightest Galaxy

October 1, 2016

Our galaxy, the Milky Way, is bigger and brighter than most others. Its hundreds of billions of stars emit roughly 20 billion times the light of the Sun. But a few rare galaxies make our galactic home seem modest. The brightest galaxy yet seen, for example, is 10,000 times brighter than the entire Milky Way.

This brilliant galaxy, which is identified only by a catalog name, is in the faint constellation Aquarius, which is low in the southeast at nightfall on these early autumn nights.

The galaxy is about 12-and-a-half billion light-years away, so we see it as it was when the universe was just 1.3 billion years old.

The galaxy owes most of its brilliance not to its stars, but to a black hole. A supermassive black hole at the galaxy's center attracts gas. As the gas plunges in, it gets so hot that it radiates profusely. Dust blocks our view of the galaxy, but the dust itself gets heated and emits infrared light. In fact, astronomers discovered the galaxy with an infrared telescope in space.

We can’t see what the galaxy looks like today. But it led such an accelerated lifestyle in its youth that it probably blew away much of its gas and converted the rest into stars. As a result, today it may be a dull type of galaxy known as a giant elliptical. If so, then it has no gas, no young stars, and no evidence that it once reigned as one of the brightest galaxies in the cosmos.


Script by Ken Croswell, Copyright 2016

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