From ALMA: “Hiding Black Hole Found”

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres


28 February, 2019

Valeria Foncea
Education and Public Outreach Officer
Joint ALMA Observatory Santiago – Chile
Phone: +56 2 2467 6258
Cell phone: +56 9 7587 1963

Masaaki Hiramatsu
Education and Public Outreach Officer, NAOJ Chile
, Tokyo – Japan
Phone: +81 422 34 3630

Calum Turner
ESO Assistant Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670

Charles E. Blue
Public Information Officer
National Radio Astronomy Observatory Charlottesville, Virginia – USA
Phone: +1 434 296 0314
Cell phone: +1 202 236 6324

Artist’s impression of a gas cloud swirling around a black hole. Credit: NAOJ

Astronomers have detected a stealthy black hole from its effects on an interstellar gas cloud. This intermediate mass black hole is one of over 100 million quiet black holes expected to be lurking in our galaxy. These results provide a new method to search for other hidden black holes and help us understand the growth and evolution of black holes.

Black holes are objects with such strong gravity that everything, including light, is sucked in and cannot escape. Because black holes do not emit light, astronomers must infer their existence from the effects their gravity produce in other objects. Black holes range in mass from about 5 times the mass of the Sun to supermassive black holes millions of times the mass of the Sun. Astronomers think that small black holes merge and gradually grow into large ones, but no one had ever found an intermediate mass, hundreds or thousands of times the mass of the Sun.

A research team led by Shunya Takekawa at the National Astronomical Observatory of Japan noticed HCN–0.009–0.044, a gas cloud moving strangely near the center of the Galaxy 25,000 light-years away from Earth in the constellation Sagittarius. They used ALMA (Atacama Large Millimeter/submillimeter Array) to perform high resolution observations of the cloud and found that it is swirling around an invisible massive object.

Takekawa explains, “Detailed kinematic analyses revealed that an enormous mass, 30,000 times that of the Sun, was concentrated in a region much smaller than our Solar System. This and the lack of any observed object at that location strongly suggests an intermediate-mass black hole. By analyzing other anomalous clouds, we hope to expose other quiet black holes. ”

Tomoharu Oka, a professor at Keio University and coleader of the team, adds, “It is significant that this intermediate mass black hole was found only 20 light-years from the supermassive black hole at the Galactic center. In the future, it will fall into the supermassive black hole; much like gas is currently falling into it. This supports the merger model of black hole growth.”

These results were published as Takekawa et al. “Indication of Another Intermediate-mass Black Hole in the Galactic Center” in The Astrophysical Journal Letters on January 20, 2019.

See the full article here .


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The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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