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Quasars II

February 6, 2013

The constellation Virgo stretches fairly high across the south at first light tomorrow. Look for its brightest star, Spica, far to the right of the bright planet Saturn.

Virgo is home to a remarkable galaxy. But the galaxy’s great distance was originally something of a puzzle. The solution showed that the galaxy is one of the brightest objects in the universe — powered by a dark source.

3c 273 looks like a fairly ordinary star. In fact, it’s bright enough to see through most telescopes. But a half-century ago, astronomer Maarten Schmidt realized that it’s much too far away to be a star — about two billion light-years.

3c 273 is a hundred times brighter than the largest “normal” galaxies, and it produces enormous amounts of radio waves. Yet most of its energy comes from a tiny region of space — only a few times wider than our solar system. Such objects are known as quasars.

A quasar is powered by gas that’s spiraling around a supermassive black hole at the heart of a galaxy. The black hole in 3c 273 is a billion times the mass of the Sun. As the gas spirals toward the black hole, it’s accelerated to a large fraction of the speed of light by the black hole’s gravity. The gas gets so hot that it produces enormous amounts of energy — it outshines entire galaxies of normal stars. So a quasar is a cosmic beacon that shines across the entire universe — powered by a black hole.

We’ll have more about quasars tomorrow.


Script by Damond Benningfield, Copyright 2012

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