Milky Way black hole spotted, sized

A colossal X-ray flare, likely sparked by a central Milky Way black hole, produced the bright spot in this Chandra image.

By Richard Stenger
CNN

(CNN) -- Direct observations are offering the first authoritative evidence that a black hole resides in the heart of our galaxy, astronomers announced Wednesday.

The Chandra X-ray Observatory, a sophisticated orbiting telescope, detected an X-ray flare leap from the center of the Milky Way, presenting almost conclusive proof of the scientific oddity.

The intense burst, heralding the fatal plunge of matter into oblivion, allowed astronomers to estimate the size of the black hole lurking in the central Milky Way at no larger than the distance between the sun and Earth.

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"This is extremely exciting because it's the first time we have seen our own neighborhood supermassive black hole devour a chunk of material," said Fred Bagonoff, who with colleagues will publish their findings in the Thursday edition of the journal Nature.

"This signal comes from closer to the event horizon of our Galaxy's supermassive black hole than any that we have ever received before. It's as if the material there sent us a postcard before it fell in," he said.

Astronomers theorize that most galactic cores have black holes, stars so massive that they collapsed into themselves, producing gravitational monsters from which nothing can escape, even light.

To study a black hole, scientists look for gas swirling around its edges like water in a whirlpool. The hapless matter, before plunging into the abyss, becomes super dense and hot, releasing intense X-ray emissions.

Circumstantial evidence had hinted that the Milky Way boasted a black hole in its center, about 24,000 light-years from Earth. But astronomers had not been able to rule out another possibility, a dense cluster of dark stars.

Until the Chandra X-ray Observatory, a NASA satellite that for two years has hunted black holes and other exotic energy phenomena, observed an X-ray flare dim and brighten for a period of only ten minutes.

Artist's conception of a black hole surrounded by a swirling ring of energy and matter in the center of our galaxy.

“It’s truly remarkable that we could identify and track this flare in such a crowded region of space,” said Mark Bautz of the Massachusetts Institute of Technology.

The variability of such emissions helps astronomers calculate the size of the regions from where they originate.

From this particular flash, Chandra researchers calculated that the mass at the center of the galaxy, about 2.6 million times that of the sun, fit into a space no larger than 93 million miles across. Only a black hole could be that dense, according to the known laws of physics.

"Baganoff and colleagues appear to have excluded all other possible alternatives," writes astronomer Fulvio Melia in an accompanying Nature article.