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Scientists investigated our galaxy's central molecular zone, which
contains the most massive, densest, and most turbulent molecular clouds
in the Milky Way. These surround the heart of our galaxy, which is
suspected to be home to a supermassive black hole about 4 million times the mass of the sun.
The central molecular zones of galaxies crowd lots of gas close
together, making them good places for stars to form. To learn more about
these lively regions, scientists used radio telescopes to compile
detailed maps of the temperature and density of clouds at the Milky
Way's heart.
Now scientists have discovered four giant clumps of gas that appear to
be the kinds of seeds intermediate-mass black holes arise from. These black holes
hundreds to thousands of times the mass of the sun that are thought to
in turn serve as the building blocks for the supermassive black holes
found in the centers of galaxies.
The clumps are each about 30,000 light-years away. One of the masses
contains the black hole suspected to exist at the heart of the Milky
Way. This disk-shaped clump is about 50 light-years across "and revolves
around the supermassive black hole at a very fast speed," said study
lead author Tomoharu Oka, an astronomer at Keio University in Japan. [Strangest Black Holes in the Universe]
The other three clumps are expanding at very fast speeds of more than
223,000 miles per hour (360,000 kilometers per hour), making the
researchers think supernova explosions were the cause of this growth,
with the fastest blooming of these clumps growing as if 200 supernovas
went off inside it. Since the age of this clump is only thought to be
about 60,000 years old, which suggests supernovas happened there every
300 years.Such a high rate of supernovas suggests that many young, massive stars are concentrated inside. The researchers estimate a massive star cluster more than 100,000 times the mass of the sun lurks within, as big as the largest star clusters in the Milky Way.
"No matter how large the star cluster is, it is very difficult to directly see the star cluster at thecenter of the Milky Way galaxy," Oka explained. "The huge amount of gas and dust lying between the solar system and the center of the Milky Way galaxy prevent not only visible light, but also infrared light, from reaching the earth. Moreover, innumerable stars in the bulge and disc of the Milky Way galaxy lie in the line of sight."
Huge star clusters at the center of the galaxy are where
intermediate-mass black holes several hundred times the mass of the sun
are expected to form.
"Many galaxies with central molecular zones may harbor such young massive clusters," Oka told SPACE.com.
"The new discovery is an important step toward unraveling the formation
and growth mechanism of the supermassive black hole at the Milky Way
galaxy's nucleus, which is a top-priority issue in galactic physics," he
added in a statement.
It remains uncertain how many intermediate-mass black holes might lurk
in the central molecular zones of galaxies, or at what rates they are
created. "Further investigations of the central molecular zones of our
galaxy and other galaxies will reveal them," Oka said. Specifically, the
Atacama Large Millimeter/sub-millimeter Array (ALMA) of radio
telescopes may detectintermediate-mass black holes, he added.
The scientists detailed their findings in the August issue of the Astrophysical Journal Supplement Series.
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