Adapted from “NASA’s NuSTAR Helps Solve Riddle of Black Hole Spin.” © 2013 by NASA.
Two X-ray space observatories, NASA’s Nuclear
Spectroscopic Telescope Array (NuSTAR) and the European
Space Agency’s XMM-Newton, have teamed up to measure,
for the first time, the spin rate of a black hole with a mass two
million times that of our sun.
The supermassive black hole lies at the dust- and gas-filled
heart of a galaxy called NGC 1365, and it is spinning almost as
fast as Einstein’s theory of gravity will allow. The findings,
which appear in a new study in the journal Nature, resolve a
long-standing debate about similar measurements in other
black holes and will lead to a better understanding of how
black holes and galaxies evolve.
“This is hugely important to the field of black hole science,”
said Lou Kaluzienski, a NuSTAR program scientist at NASA
Headquarters in Washington.
The observations also are a powerful test of Einstein’s
theory of general relativity, which says gravity can bend space-
time, the fabric that shapes our universe, and the light that
travels through it.
“We can trace matter as it swirls into a black hole using X-
rays emitted from regions very close to the black hole,” said
the coauthor of a new study, NuSTAR principal investigator
Fiona Harrison of the California Institute of Technology in
Pasadena. “The radiation we see is warped and distorted by the
motions of particles and the black hole’s incredibly strong
gravity.”
NuSTAR, an Explorer-class mission launched in June 2012,
is designed to detect the highest-energy X-ray light in great
detail. It complements telescopes that observe lower-energy X-
ray light, such as XMM-Newton and NASA’s Chandra X-ray
Observatory. Scientists use these and other telescopes to
estimate the rates at which black holes spin.
Until now, these measurements were not certain because
clouds of gas could have been obscuring the black holes and
confusing the results. With help from XMM-Newton, NuSTAR
was able to see a broader range of X-ray energies and penetrate
deeper into the region around the black hole. The new data
demonstrate that X-rays are not being warped by the clouds,
but by the tremendous gravity of the black hole. This proves
that spin rates of supermassive black holes can be determined
conclusively.
Measuring the spin of a supermassive black hole is
fundamental to understanding its past history and that of its
host galaxy.
“These monsters, with masses from millions to billions of
times that of the sun, are formed as small seeds in the early
universe and grow by swallowing stars and gas in their host
galaxies, merging with other giant black holes when galaxies
collide, or both,” said the study’s lead author, Guido Risaliti of
the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Mass., and the Italian National Institute for
Astrophysics.
Supermassive black holes are surrounded by pancake-like
accretion disks, formed as their gravity pulls matter inward.
Einstein’s theory predicts that the faster a black hole spins, the
closer the accretion disk lies to the black hole. The closer the
accretion disk is, the more gravity from the black hole will
warp X-ray light streaming off the disk.
Astronomers look for these warping effects by analyzing X-
ray light emitted by iron circulating in the accretion disk. In the
new study, they used both XMM-Newton and NuSTAR to
simultaneously observe the black hole in NGC 1365. While
XMM-Newton revealed that light from the iron was being
warped, NuSTAR proved that this distortion was coming from
the gravity of the black hole and not gas clouds in the vicinity.
NuSTAR’s higher-energy X-ray data showed that the iron was
so close to the black hole that its gravity must be causing the
warping effects.
With the possibility of obscuring clouds ruled out, scientists
can now use the distortions in the iron signature to measure the
black hole’s spin rate. The findings apply to several other black
holes as well, removing the uncertainty in the previously
measured spin rates.
Two X-ray space observatories, NASA’s Nuclear
Spectroscopic Telescope Array (NuSTAR) and the European
Space Agency’s XMM-Newton, have teamed up to measure,
for the first time, the spin rate of a black hole with a mass two
million times that of our sun.
The supermassive black hole lies at the dust- and gas-filled
heart of a galaxy called NGC 1365, and it is spinning almost as
fast as Einstein’s theory of gravity will allow. The findings,
which appear in a new study in the journal Nature, resolve a
long-standing debate about similar measurements in other
black holes and will lead to a better understanding of how
black holes and galaxies evolve.
“This is hugely important to the field of black hole science,”
said Lou Kaluzienski, a NuSTAR program scientist at NASA
Headquarters in Washington.
The observations also are a powerful test of Einstein’s
theory of general relativity, which says gravity can bend space-
time, the fabric that shapes our universe, and the light that
travels through it.
“We can trace matter as it swirls into a black hole using X-
rays emitted from regions very close to the black hole,” said
the coauthor of a new study, NuSTAR principal investigator
Fiona Harrison of the California Institute of Technology in
Pasadena. “The radiation we see is warped and distorted by the
motions of particles and the black hole’s incredibly strong
gravity.”
NuSTAR, an Explorer-class mission launched in June 2012,
is designed to detect the highest-energy X-ray light in great
detail. It complements telescopes that observe lower-energy X-
ray light, such as XMM-Newton and NASA’s Chandra X-ray
Observatory. Scientists use these and other telescopes to
estimate the rates at which black holes spin.
Until now, these measurements were not certain because
clouds of gas could have been obscuring the black holes and
confusing the results. With help from XMM-Newton, NuSTAR
was able to see a broader range of X-ray energies and penetrate
deeper into the region around the black hole. The new data
demonstrate that X-rays are not being warped by the clouds,
but by the tremendous gravity of the black hole. This proves
that spin rates of supermassive black holes can be determined
conclusively.
Measuring the spin of a supermassive black hole is
fundamental to understanding its past history and that of its
host galaxy.
“These monsters, with masses from millions to billions of
times that of the sun, are formed as small seeds in the early
universe and grow by swallowing stars and gas in their host
galaxies, merging with other giant black holes when galaxies
collide, or both,” said the study’s lead author, Guido Risaliti of
the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Mass., and the Italian National Institute for
Astrophysics.
Supermassive black holes are surrounded by pancake-like
accretion disks, formed as their gravity pulls matter inward.
Einstein’s theory predicts that the faster a black hole spins, the
closer the accretion disk lies to the black hole. The closer the
accretion disk is, the more gravity from the black hole will
warp X-ray light streaming off the disk.
Astronomers look for these warping effects by analyzing X-
ray light emitted by iron circulating in the accretion disk. In the
new study, they used both XMM-Newton and NuSTAR to
simultaneously observe the black hole in NGC 1365. While
XMM-Newton revealed that light from the iron was being
warped, NuSTAR proved that this distortion was coming from
the gravity of the black hole and not gas clouds in the vicinity.
NuSTAR’s higher-energy X-ray data showed that the iron was
so close to the black hole that its gravity must be causing the
warping effects.
With the possibility of obscuring clouds ruled out, scientists
can now use the distortions in the iron signature to measure the
black hole’s spin rate. The findings apply to several other black
holes as well, removing the uncertainty in the previously
measured spin rates.