Quasars

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A black hole a billion times as massive as the Sun lurks in the heart of the young galaxy. It's half as wide as our solar system -- a dark pit into which matter and energy can fall but never climb out.

Yet this ultimate darkness is encircled by the ultimate brightness -- a spinning disk of hot gas that's just a few times as wide as the black hole itself, but as bright as an entire galaxy of stars. This whirling maelstrom is heated to billions of degrees, so it produces enormous amounts of energy. It shines so brightly that it's visible across billions of light-years of space.

This hot bubble is a quasar -- one of the most powerful objects in the universe. Astronomers have discovered thousands of them. Most are billions of light-years away -- from a time when the universe was much younger than it is today.

They inhabit the cores of galaxies that have lots of gas and dust. Much of this material falls toward the black hole, forming the brilliant disk. Radiation from the disk can blow away much of the remaining gas and dust. That eventually shuts down the quasar. The black hole remains, but it's dark and quiet.

The radiation also shuts down the birth of new stars in the galaxy's core. In fact, there's a relationship between the mass of the black hole and the mass of the galaxy's core. That creates a "chicken-and-egg" problem about which came first -- the black hole or the surrounding galaxy. We'll talk about a possible solution tomorrow.

Script by Damond Benningfield, Copyright 2009

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