Artist’s impression of a gas cloud swirling around a black hole
Credit: NAOJ. Hi-res image
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.”
Aditional Information
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.
The Atacama Large Millimeter/submillimeter Array (ALMA), an
international astronomy facility, is a partnership of the European
Organisation for Astronomical Research in the Southern Hemisphere (ESO),
the U.S. National Science Foundation (NSF) and the National Institutes
of Natural Sciences (NINS) of Japan in cooperation with the Republic of
Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in
cooperation with the National Research Council of Canada (NRC) and the
Ministry of Science and Technology (MOST) and by NINS in cooperation
with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and
Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member
States; by the National Radio Astronomy Observatory (NRAO), managed by
Associated Universities, Inc. (AUI), on behalf of North America; and by
the National Astronomical Observatory of Japan (NAOJ) on behalf of East
Asia. The Joint ALMA Observatory (JAO) provides the unified leadership
and management of the construction, commissioning and operation of ALMA.
Contacts
Valeria Foncea
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Joint ALMA Observatory Santiago - Chile
Phone: +56 2 2467 6258
Cell phone: +56 9 7587 1963
Email: valeria.foncea@alma.cl
Masaaki Hiramatsu
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Observatory , Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp
Calum Turner
ESO Assistant Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: calum.turner@eso.org
Charles E. Blue
Public Information Officer
National Radio Astronomy Observatory Charlottesville, Virginia - USA
Phone: +1 434 296 0314
Cell phone: +1 202 236 6324
Email: cblue@nrao.edu
