Press Release

New Energy Source ‘Wrings’ Power From Black Hole Spin

By SpaceRef Editor
October 22, 2001
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Scientists for the first time have seen energy being
extracted from a black hole. Like an electric dynamo, this
black hole spins and pumps energy out through cable-like
magnetic field lines into the chaotic gas whipping around it,
making the gas — already infernally hot from the sheer force
of crushing gravity — even hotter.

Joern Wilms of Tuebingen University, Germany, and an
international team of astronomers observed the novel “power
tapping” with the European Space Agency’s X-ray Multi-Mirror
Mission (XMM-Newton) satellite by watching a supermassive
black hole in the core of galaxy named MCG-6-30-15. The
observation also may explain the origin of particle jets in
quasars.

“Never before have we seen energy extracted from a black
hole,” said co-author Christopher Reynolds of the University
of Maryland, College Park. “We always see energy going in, not
out.”

“The gravity in this region appears to be so intense that the
very fabric of space twists around the black hole, dragging
magnetic field lines along with it,” said Wilms. “The magnetic
fields tighten about the black hole, slowing its spin. This
‘friction’ heats the region to even higher temperatures.”

Scientists say most galaxies, including our Milky Way galaxy,
have a supermassive black hole at their core. A supermassive
black hole contains the mass of millions to billions of Suns
compressed within a region smaller than our solar system. The
black hole in MCG-6-30-15, over 100 million light-years from
Earth, has the mass of about 100 million Suns.

The team observed the X-ray glow of iron gas traveling about
half the speed of light very close to the black hole in MCG-6-
30-15’s event horizon, the theoretical border of a black hole.
XMM-Newton captured the spectrum, or chemical fingerprint, of
this gas. The spectrum, laid out on a graph, resembles an
electrocardiogram with its spikes and dips.

The iron spectrum from MCG-6-30-15 has extremely broad
“spikes,” an indication of gravity tugging at the particles of
light, called photons, and literally stretching the light. MCG
6-30-15’s iron line was so broad, in fact, that the bulk of
the light must emanate from very close to the black hole,
where the force of gravity is the greatest, Reynolds said.

The total energy output, or luminosity indicated by the
spectrum, however, was too bright to be powered by gravity and
the free fall of matter alone. Some additional power source
must exist to boost the luminosity to the observed intensity.

Co-author Mitchell Begelman of the University of Colorado,
Boulder, said this finding may be observational evidence of a
theory by Prof. Roger Blandford, currently at the California
Institute of Technology, Pasadena, and Dr. Roman Znajek, when
he was at Cambridge University in England, over 25 years ago.
According to the theory, rotational energy can be extracted
from the black hole as it is braked by magnetic fields. The
first law of thermodynamics (conservation of energy) states
that energy lost from the black hole must be absorbed by the
region.

Begelman said the energy lost in MCG-6-30-15 is transferred to
the inner edge of the accretion disk, a flow of gas swirling
around and eventually falling into the black hole. The
Blandford-Znajek theory implies that energy flows to particle
jets emanating perpendicularly from the accretion disk in
certain supermassive black hole systems called quasars. MCG
6-30-15 is not a quasar, but Begelman said the theory can
still apply because it predicts that the magnetic field might
also link to the disk.

ASCA, a Japanese X-ray satellite, found possible evidence of a
spinning black hole in 1994, but the signal was too weak to
observe any evidence of energy being extracted from the black
hole.

XMM-Newton, launched from French Guiana by ESA in December
1999, carries three advanced X-ray telescopes with the light-
collecting ability to detect millions of sources, far greater
than any previous X-ray mission. NASA helped fund mission
development and supports guest observatory time. NASA’s
Goddard Space Flight Center, Greenbelt, Md., hosts the U.S.
guest-observer support center.

Images are available at:
http://www.gsfc.nasa.gov/topstory/20011015blackhole.html

SpaceRef staff editor.