Scientists have used NASA's Nuclear Spectroscopic Telescope Array
(NuSTAR), an orbiting X-ray telescope, to capture an extreme and rare
event in the regions immediately surrounding a supermassive black hole. A
compact source of X-rays that sits near the black hole, called the
corona, has moved closer to the black hole over a period of just days.
The researchers publish their results in Monthly Notices of the Royal Astronomical Society.
"The corona recently collapsed in towards the black hole, with the
result that the black hole's intense gravity pulled all the light down
onto its surrounding disk, where material is spiralling inward," said
Michael Parker of the Institute of Astronomy in Cambridge, lead author of the new paper.
As the corona shifted closer to the black hole, the black hole's
gravitational field exerted a stronger tug on the x-rays emitted by the
corona. The result was an extreme blurring and stretching of the X-ray
light. Such events had been observed previously, but never to this
degree and in such detail.
Supermassive black holes
are thought to reside in the centres of all galaxies. Some are more
massive and rotate faster than others. The black hole in this new study,
referred to as Markarian 335, or Mrk 335, is about 324 million
light-years from Earth in the direction of the Pegasus constellation. It
is one of the most extreme systems of which the mass and spin rate have
ever been measured. The black hole squeezes about 10 million times the
mass of our Sun into a region only 30 times as wide as the Sun's
diameter, and it spins so rapidly that space and time are dragged around
with it.
Even though some light falls into a supermassive black hole never to
be seen again, other high-energy light emanates from both the corona and
the surrounding accretion disk of superheated material. Though
astronomers are uncertain of the shape and temperature of coronas, they
know that they contain particles that move close to the speed of light.
NASA's Swift
satellite has monitored Mrk 335 for years, and recently noted a
dramatic change in its X-ray brightness. In what is called a
'target-of-opportunity' observation, NuSTAR was redirected to take a
look at high-energy X-rays from this source in the range of 3 to 79 kiloelectron volts.
This particular energy range offers astronomers a detailed look at what
is happening near the event horizon, the region around a black hole
from which light can no longer escape gravity's grasp.
Follow-up observations indicate that the corona still is in this
close configuration, months after it moved. Researchers don't know
whether and when the corona will shift back. What is more, the NuSTAR
observations reveal that the grip of the black hole's gravity pulled the
corona's light onto the inner portion of its superheated disk, better
illuminating it. The shifting corona lit up the precise region they
wanted to study, almost as if somebody had shone a flashlight for the
astronomers.
The new data could ultimately help determine more about the
mysterious nature of black hole coronas. In addition, the observations
have provided better measurements of Mrk 335's furious relativistic spin
rate. Relativistic speeds are those approaching the speed of light, as
described by Albert Einstein's theory of relativity.
"We still don't understand exactly how the corona is produced or why
it changes its shape, but we see it lighting up material around the
black hole, enabling us to study the regions so close in that effects
described by Einstein's theory of general relativity become prominent,"
said NuSTAR Principal Investigator Fiona Harrison of the California
Institute of Technology (Caltech)
in Pasadena. "NuSTAR's unprecedented capability for observing this and
similar events allows us to study the most extreme light-bending effects
of general relativity."
Media contacts
J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
Whitney Clavin
Jet Propulsion Laboratory
Pasadena
California
United States
Tel: +1 818 354 4673
whitney.clavin@jpl.nasa.gov
Science contact
Prof Michael Parker
Institute of Astronomy
Cambridge
United Kingdom
Tel: +44 (0)1223 337 511
mlparker@ast.cam.ac.uk
Further information
The new work appears in B. Agís-González et al., 2014, "Black hole spin and size of the X-ray-emitting region(s) in the Seyfert 1.5 galaxy ESO 362−G18", Monthly Notices of the Royal Astronomical Society, vol. 443, pp. 2862-2873, published by Oxford University Press. The paper is available free of charge via the link.
Notes for editors
NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory (JPL) in Pasadena for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia. Its instrument was built by a consortium including Caltech, JPL, the University of California, Berkeley, Columbia University, New York, NASA's Goddard Space Flight Center, Greenbelt, Maryland, the Danish Technical University in Denmark, Lawrence Livermore National Laboratory in Livermore, California, ATK Aerospace Systems in Goleta, California, and with support from the Italian Space Agency (ASI) Science Data Center.
NuSTAR's mission operations centre is at UC Berkeley, with the ASI
providing its equatorial ground station located in Malindi, Kenya. The
mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.
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Source: Royal Astronomical Society (RAS)
