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Indian-American
detects black holes with 10 billion times sun's mass
Indo-Asian
News Service
Washington, Sep 12 (IANS) There are limits to how big super
gigantic black holes can grow, according to the latest research
led by an Indian-American astrophysicist of Yale University.
These "ultra-massive" black holes have been shown
to have masses upwards of one billion times that of our own
Sun, which is where they have set the limit on themselves.
Priyamvada Natarajan, associate professor of astronomy at
Yale and Ezequiel Treister, a postdoctoral fellow at Hawaii
University, have shown that even the biggest of these gravitational
monsters can't keep growing forever.
Instead, they appear to curb their own growth - once they
accumulate about 10 billion times the mass of the Sun.
These black holes, found at the centres of giant elliptical
galaxies in huge galaxy clusters, are the biggest in the known
universe.
Even the large black hole at the centre of our own Milky Way
galaxy is thousands of times smaller these behemoths. But
these gigantic black holes, which accumulate mass by sucking
in matter from neighbouring gas, dust and stars, seem unable
to grow beyond this limit regardless of where - and when -
they appear in the universe.
"It's not just happening today," said Natarajan.
"They shut off at every epoch in the universe."
Natarajan and Treister used existing optical and X-ray data
of these ultra-massive black holes to show that, in order
for those various observations to be consistent, the black
holes must essentially shut off at some point in their evolution.
One possible explanation put forth by Natarajan is that the
black holes eventually reach the point when they radiate so
much energy as they consume their surroundings that they end
up interfering with the very gas supply that feeds them, which
may interrupt nearby star formation.
"Evidence has been mounting for the key role that black
holes play in the process of galaxy formation," said
Natarajan. "But it now appears that they are likely the
prima donnas of this space opera."
These findings will appear in the Monthly Notices of the Royal
Astronomical Society (MNRAS).
Indo-Asian News Service
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