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Balls of gas losing energy form black holes
By Hope Babowice | Daily Herald Columnist

A black hole is a star that is so massive and dense that nothing, not even light, can escape.


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Published: 6/23/2010 12:00 AM

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The Warren-Newport Public Library in Gurnee suggests these titles on black holes:

• "The Mysterious Universe: Supernovas, Dark Energy and Black Holes," by Ellen B. Jackson

• "Black Holes and Other Bizarre Space Objects," by David Jefferis

• "Black Holes," by Dana Meachen Rau

• "Black Holes, Pulsars and Quasars," by Isaac Asimov

• "The Mystery of Black Holes," by Chris Oxlade

Fifth-grade students in Elise Diaz's class at O'Plaine School in Gurnee asked: "How are black holes formed?"

The concept of a star that is so massive and dense that nothing, not even light, could escape was first proposed by English scientist John Michell in 1784, but it wasn't until the last few decades that we have had good evidence they actually exist. The phrase "black hole" was first coined by John Wheeler in the late 1960s. Wheeler was the physicist and professor who also developed the term "wormhole."

Think of something so incredibly dense. Now think of something so dense that it is crushed into a single point and nothing remains but its gravity. That's what we call a black hole. These space objects can only be identified if objects surrounding them move in an unusual pattern. They can't be photographed or observed directly with a telescope. Another clue that a black hole could be present is the detection of extremely high temperatures and radiation that would be given off by the gas and dust that are sucked into a black hole.

There are two types of black holes, said Geza Gyuk, director of the Adler Planetarium: Stellar black holes and supermassive black holes.

In the life cycle of a massive star, the ball of gas eventually uses up all of its energy. Gyuk said, "Unfortunately for the massive stars, at the very end of their life there is no further source of energy that can stop the collapse once it starts and the core just keeps getting smaller and the gravity keeps getting stronger. Eventually the whole core, more massive than a million Earths, gets crushed into a space only a few miles across. The gravity becomes so strong that nothing, not even light, can escape."

A stellar black hole is a few times the size of the sun. A supermassive black hole ranges in size from a few hundred thousand times the mass of the sun to a few billion times the mass of the sun.

One of the many mysteries surrounding black holes is that we don't really know where supermassive black holes come from. An educated guess, Gyuk said, is that supermassive black holes start in very dense clusters of stars. "Somehow many smaller stellar black holes are merged to form a supermassive black hole."