2020
January
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Strange objects at the center of the Milky Way

Sometimes they behave like a cloud of gas and then they’ll start behaving again almost like an ordinary star: the so-called “G-objects,” which astronomers describe in an article in the scientific journal Nature, are hard to fit into any single category. Six of these objects have already been identified by researchers. They were all found in the direct vicinity of the center of our Milky Way – orbiting the supermassive black hole, Sagittarius A*.

This point of commonality probably also contributes to their strange behavior. G1 to G6 have orbits that lead them around the black hole once every 100 to 1000 years. Whenever they get close to the black hole, they are stretched like chewing gum by its gravity, and then they apparently contract again as they move farther away.

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In the early universe, a hydrogen diet made black holes fat

Only a billion years after the big bang, there were already galaxies whose centers harbored supermassive black holes several billion times the mass of our Sun. Astronomers know this from observations of far distant quasars and active galaxies. But how were the black holes able to grow so large so quickly? The problem seemed even more complicated, because earlier observations with ALMA, the Atacama Large Millimeter/Submillimeter Array, had shown a lot of dust and gas in these early galaxies, which promoted rapid star formation. However, if a lot of stars were created, there would have been little left over to feed a black hole.

The solution: the young giants were fed from huge reserves of cold hydrogen gas. This finding was discovered by astronomers using the European Southern Observatory’s Very Large Telescope.

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