Astronomers
are getting a close-up look at a cosmic eating machine: a spinning black hole
that devours the mass equivalent of two Earths per hour, verging on the limit
of its feeding ability.
Supermassive
black holes can weigh as much as a billion
suns or more and are thought to reside at the centers of most, if not all,
large galaxies. Their gravity is so powerful it traps even light, making black
holes invisible. Their presence is inferred by watching the motions of
stars and gas around them, along with the radiation that's generated in their
frenzied vicinities.
The
behemoth of interest in the new close-up study, which will be published in the
May 28 issue of the journal Nature, lies at the center of a distant
active galaxy known as 1H0707-495. Using data from the European Space Agency's XMM-Newton
observatory, astronomers analyzed X-rays emitted during the black hole's feeding
frenzy.
As matter
swirls in toward a black hole, gravity makes it travel at significant fractions
of light-speed. That generates X-rays and other radiation that can give
astronomers information about the spin of the black hole and its size, among
other details.
In this
case, the astronomers say they are tracking matter that's within twice the
radius of the black hole itself.
Specifically,
the XMM-Newton detections suggested the galaxy's core is much richer in iron
than the rest of the galaxy. In addition, there was a time lag of 30 seconds
between changes in the X-ray light observed directly and those seen in its
reflection from the disk. From this delay, the astronomers estimate the black
hole weighs about 3 million to 5 million solar masses – modest by supermassive
black hole standards.
The team will
continue to track the galaxy and map out the accreting
process of this supermassive black hole. Far from being a steady process, like
muddy water slipping down a plughole, a feeding black hole is a messy eater.
"Accretion
is a very messy process because of the magnetic fields that are involved,"
said study scientist Andrew Fabian of the University of Cambridge.
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