Milky Way enigma: Why galaxy’s central black hole is silent

Sagittarius A

An image released by NASA Tuesday, shows Sagittarius A, the supermassive black hole at the center of the Milky Way Galaxy made from data provided by the Chandra X-ray Observatory. Credit: NASA/AP

One of the Milky Way’s longstanding puzzles centers on the super-massive black hole at its core, in the constellation Sagittarius: Why is that monstrous black hole, known as Sag A*, so much less energetic that its counterparts in other galaxies?

The behemoth, with some 2.6 million times the sun’s mass, is a cosmic dud at the moment. Something is starving it, depriving it of material that otherwise would plummet into it.

Roman Shcherbakov, a researcher at the Harvard-Smithsonian Center for Astrophysics, says he’s figured out what that “something” is likely to be: heat.

As material from surrounding stars approaches the black hole and gets compressed by the monster’s gravity, it heats up. Some of that heat gets conducted away from the black hole, setting up a source of pressure that sweeps material away from the voracious object.

In other words, heating around the black hole’s event horizon – essentially the boundary within which material falls into oblivion – is in effect starving the black hole.

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