Friday, February 3, 2017

Conditions Right For Stars, Planets Near Milky Way’s Supermassive Black Hole

Clouds of gas (white box), observed with Atacama Large Millimeter/submillimeter Array (ALMA), appear to have the right mass to be young stars, even though they aren’t far from the supermassive black hole at the center of the Milky Way (green dot). Courtesy of F. Yusef-Zadeh

Blobs of gas near the Milky Way’s center may be just the right mass to harbor young stars and possibly planets, too. Any such budding stellar systems would face an uphill battle, developing only about two light-years from the galaxy’s central supermassive black hole with its intense gravity and ultraviolet radiation. But it’s not impossible for the small stars to survive in the hostile place, a new study suggests.

“Nature is very clever. It finds ways to work in extreme environments,” says Farhad Yusef-Zadeh, physics and astronomy and an associated at the Center for Interdisciplinary Exploration and Research in Astrophysics. Four blobs of gas near the galactic center have the right amount of mass to be planetary systems with small, young stars, Yusef-Zadeh and colleagues report in a paper slated for publication in the Monthly Notices of the Royal Astronomical Society.

“It is fairly likely that planets and low-mass stars do form near the galactic center. But we do not know it for sure at the moment,” says Avi Loeb, an astrophysicist at Harvard University. Loeb, who was not involved in the study.

Yusef-Zadeh and colleagues used ALMA, the Atacama Large Millimeter/submillimeter Array, in Chile to study emissions from five of the 44 blobs of gas that the team discovered in 2014 (SN Online: 3/24/15). Four of the clouds had between 0.03 and 0.05 as much mass as the sun, the team calculated. That’s right in line with what’s needed to generate low-mass stars — ones about the size of the sun or a little bigger — and the planets that orbit them, Yusef-Zadeh says. He points out that the team has not detected these stars or planets, just that conditions are ripe for them to exist.

Loeb notes that the team had to infer the clouds’ entire masses from the ALMA measurements, which may reveal only a surface look at the blobs. The clouds may actually be denser; as a result, they would form more massive stars, challenging the team’s claim that low-mass stars are forming.

Yusef-Zadeh and colleagues are planning additional studies with ALMA and are also working on research that suggests that black holes may, in fact, help star formation. “It’s paradoxical,” Yusef-Zadeh says. “Black holes eat everything that comes too close to them. They tear everything apart. But they may actually make the formation of stars more efficient.”

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