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 corona recently collapsed in toward 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 Cambridge’s Institute of Astronomy, lead author of a paper on the findings which appears in the journal Monthly Notices of the Royal Astronomical Society.
As the corona shifted closer to the black hole, the gravity of the black hole exerted a stronger tug on the x-rays emitted by it. 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 of the systems for 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 the diameter of the sun, 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. Almost as if somebody had shone a flashlight for the astronomers, the shifting corona lit up the precise region they wanted to study.
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.”
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.
NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has captured an extreme and rare event in the regions immediately surrounding a supermassive black hole.NASABlack Holes: Monsters in Space (Artist's Concept)
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Astronomy: Another super-Earth found
Nature 512, 7513 (2014). doi:10.1038/512116c
A 'super-Earth' planet — an extrasolar planet larger than Earth but smaller than Neptune — has been detected in the habitable zone of a star called Gliese 832.Robert Wittenmyer at the University of New South Wales in Sydney, Australia, and his colleagues used data
Solar system: Sandcastles in space
Nature 512, 7513 (2014). doi:10.1038/512139a
Authors: Daniel J. Scheeres
Analysis of a kilometre-sized, near-Earth asteroid shows that forces weaker than the weight of a penny can keep it from falling apart. This has implications for understanding the evolution of the Solar System. See Letter p.174
Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA
Nature 512, 7513 (2014). doi:10.1038/nature13632
Authors: Ben Rozitis, Eric MacLennan & Joshua P. Emery
Space missions and ground-based observations have shown that some asteroids are loose collections of rubble rather than solid bodies. The physical behaviour of such ‘rubble-pile’ asteroids has been traditionally described using only gravitational and frictional forces within a granular material. Cohesive forces in the form of small van der Waals forces between constituent grains have recently been predicted to be important for small rubble piles (ten kilometres across or less), and could potentially explain fast rotation rates in the small-asteroid population. The strongest evidence so far has come from an analysis of the rotational breakup of the main-belt comet P/2013 R3 (ref. 7), although that was indirect and poorly constrained by observations. Here we report that the kilometre-sized asteroid (29075) 1950 DA (ref. 8) is a rubble pile that is rotating faster than is allowed by gravity and friction. We find that cohesive forces are required to prevent surface mass shedding and structural failure, and that the strengths of the forces are comparable to, though somewhat less than, the forces found between the grains of lunar regolith.
Astronomical instrumentation: Atmospheric blurring has a new enemy
Nature 512, 7513 (2014). doi:10.1038/512144a
Authors: Brent Ellerbroek
A fully automated optics system that corrects atmospheric blurring of celestial objects has imaged 715 star systems thought to harbour planets, completing each observation in less time than it takes to read this article.
Interacting supernovae from photoionization-confined shells around red supergiant stars
Nature 512, 7514 (2014). doi:10.1038/nature13522
Authors: Jonathan Mackey, Shazrene Mohamed, Vasilii V. Gvaramadze, Rubina Kotak, Norbert Langer, Dominique M.-A. Meyer, Takashi J. Moriya & Hilding R. Neilson
Betelgeuse, a nearby red supergiant, is a fast-moving star with a powerful stellar wind that drives a bow shock into its surroundings. This picture has been challenged by the discovery of a dense and almost static shell that is three times closer to the star than the bow shock and has been decelerated by some external force. The two physically distinct structures cannot both be formed by the hydrodynamic interaction of the wind with the interstellar medium. Here we report that a model in which Betelgeuse’s wind is photoionized by radiation from external sources can explain the static shell without requiring a new understanding of the bow shock. Pressure from the photoionized wind generates a standing shock in the neutral part of the wind and forms an almost static, photoionization-confined shell. Other red supergiants should have much more massive shells than Betelgeuse, because the photoionization-confined shell traps up to 35 per cent of all mass lost during the red supergiant phase, confining this gas close to the star until it explodes. After the supernova explosion, massive shells dramatically affect the supernova light curve, providing a natural explanation for the many supernovae that have signatures of circumstellar interaction.