Runaway Star Might Explain Black Hole's Disappearing Act More About the Missions

This illustration shows a black hole surrounded by a disk of gas. In the left panel, a streak of debris falls toward the disk. In the right panel, the debris has dispersed some of the gas, causing the corona (the ball of white light above the black hole) to disappear.Credits: NASA/JPL-Caltech

The telltale sign that the black hole was feeding vanished, perhaps when a star interrupted the feast. The event could lend new insight into these mysterious objects.

At the center of a far-off galaxy, a black hole is slowly consuming a disk of gas that swirls around it like water circling a drain. As a steady trickle of gas is pulled into the gaping maw, ultrahot particles gather close to the black hole, above and below the disk, generating a brilliant X-ray glow that can be seen 300 million light-years away on Earth. These collections of ultrahot gas, called black hole coronas, have been known to exhibit noticeable changes in their luminosity, brightening or dimming by up to 100 times as a black hole feeds.

But two years ago, astronomers watched in awe as X-rays from the black hole corona in a galaxy known as 1ES 1927+654 disappeared completely, fading by a factor of 10,000 in about 40 days. Almost immediately it began to rebound, and about 100 days later had become almost 20 times brighter than before the event.

The X-ray light from a black hole corona is a direct byproduct of the black hole's feeding, so the disappearance of that light from 1ES 1927+654 likely means that its food supply had been cut off. In a new study in the Astrophysical Journal Letters, scientists hypothesize that a runaway star might have come too close to the black hole and been torn apart. If this was the case, fast-moving debris from the star could have crashed through part of the disk, briefly dispersing the gas.

"We just don't normally see variations like this in accreting black holes," said Claudio Ricci, an assistant professor at Diego Portales University in Santiago, Chile, and lead author of the study. "It was so strange that at first we thought maybe there was something wrong with the data. When we saw it was real, it was very exciting. But we also had no idea what we were dealing with; no one we talked to had seen anything like this."

Nearly every galaxy in the universe may host a supermassive black hole at its center, like the one in 1ES 1927+654, with masses millions or billions of times greater than our Sun. They grow by consuming the gas encircling them, otherwise known as an accretion disk. Because black holes don't emit or reflect light, they can't be seen directly, but the light from their coronas and accretion disks offers a way to learn about these dark objects.

The authors' star hypothesis is also supported by the fact that a few months before the X-ray signal disappeared, observatories on Earth saw the disk brighten considerably in visible-light wavelengths (those that can be seen by the human eye). This might have resulted from the initial collision of the stellar debris with the disk.

Digger Deeper

The disappearing event in 1ES 1927+654 is unique not only because of the dramatic change in brightness, but also because of how thoroughly astronomers were able to study it. The visible-light flare prompted Ricci and his colleagues to request follow-up monitoring of the black hole using NASA's Neutron star Interior Composition Explorer (NICER), an X-ray telescope aboard the International Space Station. In total, NICER observed the system 265 times over 15 months. Additional X-ray monitoring was obtained with NASA's Neil Gehrels Swift Observatory – which also observed the system in ultraviolet light – as well as NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the ESA (the European Space Agency) XMM-Newton observatory (which has NASA involvement).

When the X-ray light from the corona disappeared, NICER and Swift observed lower-energy X-rays from the system so that, collectively, these observatories provided a continuous stream of information throughout the event.

Although a wayward star seems the most likely culprit, the authors note that there could be other explanations for the unprecedented event. One remarkable feature of the observations is that the overall drop in brightness wasn't a smooth transition: Day to day, the low-energy X-rays NICER detected showed dramatic variation, sometimes changing in brightness by a factor of 100 in as little as eight hours. In extreme cases, black hole coronas have been known to become 100 times brighter or dimmer, but on much longer timescales. Such rapid changes occurring continuously for months was extraordinary.

"This dataset has a lot of puzzles in it," said Erin Kara, an assistant professor of physics at the Massachusetts Institute of Technology and a coauthor of the new study. "But that's exciting, because it means we're learning something new about the universe. We think the star hypothesis is a good one, but I also think we're going to be analyzing this event for a long time."

It's possible that this kind of extreme variability is more common in black hole accretion disks than astronomers realize. Many operating and upcoming observatories are designed to search for short-term changes in cosmic phenomena, a practice known as "time domain astronomy," which could reveal more events like this one.

"This new study is a great example of how flexibility in observation scheduling allows NASA and ESA missions to study objects that evolve relatively quickly and look for longer-term changes in their average behavior," said Michael Loewenstein, a coauthor of the study and an astrophysicist for the NICER mission at the University of Maryland College Park and NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. "Will this feeding black hole return to the state it was in before the disruption event? Or has the system been fundamentally changed? We're continuing our observations to find out."

More About the Missions

NICER is an Astrophysics Mission of Opportunity within NASA's Explorer program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined and efficient management approaches within the heliophysics and astrophysics science areas.

NuSTAR recently celebrated eight years in space, having launched on June 13, 2012. A Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Southern California for the agency's Science Mission Directorate in Washington, NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp. in Dulles, Virginia. NuSTAR's mission operations center is at the University of California, Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center at GSFC. ASI provides the mission's ground station and a mirror data archive. Caltech manages JPL for NASA.

ESA's XMM-Newton observatory was launched in December 1999 from Kourou, French Guiana. NASA funded elements of the XMM-Newton instrument package and provides the NASA Guest Observer Facility at GSFC, which supports use of the observatory by U.S. astronomers.

GSFC manages the Swift mission in collaboration with Penn State in University Park, Pennsylvania, the Los Alamos National Laboratory in New Mexico and Northrop Grumman Innovation Systems in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory of the University College London in the United Kingdom, Brera Observatory in Italy, and the Italian Space Agency.

Editor: Tony Greicius

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For more information on NuSTAR, visit: https://www.nasa.gov/mission_pages/nustar/main/index.html / https://www.nustar.caltech.edu/

For more information on NICER, visit: https://www.nasa.gov/nicer / https://nicer.gsfc.nasa.gov

For more information on Swift, visit:https://www.nasa.gov/mission_pages/swift/main / https://swift.gsfc.nasa.gov/

For more information on XMM-Newton, visit:  https://www.nasa.gov/xmm-newton
 

Source: NASA/Nustar

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In Colliding Galaxies, a Pipsqueak Shines Bright

Bright green sources of high-energy X-ray light captured by NASA's NuSTAR mission are overlaid on an optical-light image of the Whirlpool galaxy (in the center of the image) and its companion galaxy, M51b (the bright greenish-white spot above the Whirlpool), taken by the Sloan Digital Sky Survey.Credit: NASA/JPL-Caltech, IPAC.  › Larger view

In the nearby Whirlpool galaxy and its companion galaxy, M51b, two supermassive black holes heat up and devour surrounding material. These two monsters should be the most luminous X-ray sources in sight, but a new study using observations from NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) mission shows that a much smaller object is competing with the two behemoths.

The most stunning features of the Whirlpool galaxy - officially known as M51a - are the two long, star-filled "arms" curling around the galactic center like ribbons. The much smaller M51b clings like a barnacle to the edge of the Whirlpool. Collectively known as M51, the two galaxies are merging. 

At the center of each galaxy is a supermassive black hole millions of times more massive than the Sun. The galactic merger should push huge amounts of gas and dust into those black holes and into orbit around them. In turn, the intense gravity of the black holes should cause that orbiting material to heat up and radiate, forming bright disks around each that can outshine all the stars in their galaxies. 

But neither black hole is radiating as brightly in the X-ray range as scientists would expect during a merger. Based on earlier observations from satellites that detect low-energy X-rays, such as NASA's Chandra X-ray Observatory, scientists believed that layers of gas and dust around the black hole in the larger galaxy were blocking extra emission. But the new study, published in the Astrophysical Journal, used NuSTAR's high-energy X-ray vision to peer below those layers and found that the black hole is still dimmer than expected. 

"I'm still surprised by this finding," said study lead author Murray Brightman, a researcher at Caltech in Pasadena, California. "Galactic mergers are supposed to generate black hole growth, and the evidence of that would be strong emission of high-energy X-rays. But we're not seeing that here."

Brightman thinks the most likely explanation is that black holes "flicker" during galactic mergers rather than radiate with a more or less constant brightness throughout the process. 

"The flickering hypothesis is a new idea in the field," said Daniel Stern, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena and the project scientist for NuSTAR. "We used to think that the black hole variability occurred on timescales of millions of years, but now we're thinking those timescales could be much shorter. Figuring out how short is an area of active study."

Small but  Brilliant

Along with the two black holes radiating less than scientists anticipated in M51a and M51b, the former also hosts an object that is millions of times smaller than either black hole yet is shining with equal intensity. The two phenomena are not connected, but they do create a surprising X-ray landscape in M51. 

The small X-ray source is a neutron star, an incredibly dense nugget of material left over after a massive star explodes at the end of its life. A typical neutron star is hundreds of thousands of times smaller in diameter than the Sun - only as wide as a large city - yet has one to two times the mass. A teaspoon of neutron star material would weigh more than 1 billion tons. 

Despite their size, neutron stars often make themselves known through intense light emissions. The neutron star found in M51 is even brighter than average and belongs to a newly discovered class known as ultraluminous neutron stars. Brightman said some scientists have proposed that strong magnetic fields generated by the neutron star could be responsible for the luminous emission; a previous paper by Brightman and colleagues about this neutron star supports that hypothesis. Some of the other bright, high-energy X-ray sources seen in these two galaxies could also be neutron stars. 

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia (now part of Northrop Grumman). NuSTAR's mission operations center is at UC Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. Caltech manages JPL for NASA

News Media Contact

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

Source: NuSTAR/News

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NASA's NuSTAR sees rare blurring of black hole light

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.

An artist’s impression of a supermassive black hole and its surroundings. The regions around supermassive black holes shine brightly in X-rays. Some of this radiation comes from a surrounding disk, and most comes from the corona, pictured here as the white light at the base of a jet. This is one possible configuration for the Mrk 335 corona, as its actual shape is unclear. Credit: NASA-JPL / Caltech. Click here a full resolution image

"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.

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3800 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others. Follow the RAS on Twitter via @royalastrosoc

Source: Royal Astronomical Society (RAS)

Supernovas Slosh Before Exploding

A longstanding mystery of astronomy, how supernovas explode, might finally have been solved with the help of NASA's Nuclear Spectroscopic Telescope Array (NuSTAR).  The high-energy X-ray observatory has mapped radioactive material in the supernova remnant Cassiopeia A (Cas A).  The map reveals how shock waves likely rip massive dying stars apart--by sloshing.

"Stars are spherical balls of gas, and so you might think that when they end their lives and explode, that explosion would look like a uniform ball expanding out with great power," said Fiona Harrison, the principal investigator of NuSTAR at Caltech. "Our new results show how the explosion's heart, or engine, is distorted, possibly because the inner regions literally slosh around before detonating."

Harrison is a co-author of a paper about the results appearing in the Feb. 20 issue of Nature.

In this false-color X-ray image of CAS A, blue traces the distribution of radioactive titanium-44, which is produced in the heart of the supernova. More

NuSTAR has helped decide between two competing models of supernova explosions: Jets vs. Sloshing. More

How supernovas explode has been a mystery for a long time: video. When researchers simulate supernova blasts using computers, as a massive star dies and collapses, the main shock wave often stalls out and the star fails to shatter. The latest findings strongly suggest the exploding star literally sloshed around, re-energizing the stalled shock wave and allowing the star to finally blast off its outer layers. 

NuSTAR's target, Cas A, was created when a massive star blew up as a supernova leaving a dense stellar corpse and its ejected remains. The light from the explosion reached Earth a few hundred years ago, so we are seeing the stellar remnant when it was fresh and young.

"With NuSTAR we have a new forensic tool to investigate the explosion," said the paper's lead author, Brian Grefenstette of Caltech. "Previously, it was hard to interpret what was going on in Cas A because the material that we could see only glows in X-rays when it's heated up. Now that we can see the radioactive material, which glows in X-rays no matter what, we are getting a more complete picture of what was going on at core of the explosion." 

NuSTAR is the first telescope capable of producing maps of radioactive elements in supernova remnants. In this case, the element is titanium-44, which has an unstable nucleus produced at the heart of the exploding star. The NuSTAR map of Cas A shows titanium concentrated in clumps at the remnant's center, which suggests a sloshing action. 

The NuSTAR map also casts doubt on other models of supernova explosions, in which the star is rapidly rotating just before it dies and launches narrow streams of gas that drive the stellar blast. Though imprints of jets have been seen before around Cas A, it was not known if they were triggering the explosion. NuSTAR did not see the titanium, essentially the radioactive ash from the explosion, in narrow regions matching the jets, so the jets were not the explosive trigger. 

"This is why we built NuSTAR," said Paul Hertz, director of NASA's astrophysics division in Washington. "To discover things we never knew -- and did not expect -- about the high-energy universe." 

Credits:

Production editor: Dr. Tony Phillips | Credit: Science@NASA

More information:

Why Won't the Supernova Explode?  -- this ScienceCast video explores the longstanding mystery of supernova explosions

Supernovas seed the universe with many elements, including the gold in jewelry, the calcium in bones and the iron in blood. While small stars like our sun die less violent deaths, stars at least eight times as massive as our sun blow up in supernova explosions. The high temperatures and particles created in the blast fuse light elements together to create heavier elements.  Learn more

NuSTAR home page

 Source: NASA - Science News

Dead Star and Distant Black Holes Dazzle in X-Rays

Can you see the shape of a hand in this new X-ray image? The hand might look like an X-ray from the doctor's office, but it is actually a cloud of material ejected from a star that exploded. Image Credit: NASA/JPL-Caltech/McGill. Full image and caption

A range of supermassive black holes lights up this new image from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. All of the dots are active black holes tucked inside the hearts of galaxies, with colors representing different energies of X-ray light. Image Credit: NASA/JPL-Caltech/Yale University. Full image and caption

 

Two new views from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, showcase the telescope's talent for spying objects near and far. One image shows the energized remains of a dead star, a structure nicknamed the "Hand of God" after its resemblance to a hand. Another image shows distant black holes buried in blankets of dust.

"NuSTAR's unique viewpoint, in seeing the highest-energy X-rays, is showing us well-studied objects and regions in a whole new light," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology in Pasadena, Calif.

NuSTAR launched into space June 13, 2012, on a mission to explore the high-energy X-ray universe. It is observing black holes, dead and exploded stars and other extreme objects in our own Milky Way galaxy and beyond.

The new "Hand of God" image shows a nebula 17,000 light-years away, powered by a dead, spinning star called PSR B1509-58, or B1509 for short. The dead star, called a pulsar, is the leftover core of a star that exploded in a supernova. The pulsar is only about 19 kilometers (12 miles) in diameter but packs a big punch: it is spinning around nearly seven times every second, spewing particles into material that was upheaved during the star's violent death. These particles are interacting with magnetic fields around the ejected material, causing it to glow with X-rays. The result is a cloud that, in previous images, looked like an open hand.

One of the big mysteries of this object, called a pulsar wind nebula, is whether the pulsar's particles are interacting with the material in a specific way to make it appear as a hand, or if the material is in fact shaped like a hand.

"We don't know if the hand shape is an optical illusion," said Hongjun An of McGill University, Montreal, Canada. "With NuSTAR, the hand looks more like a fist, which is giving us some clues."

The second image from NuSTAR shows active, supermassive black holes between three and 10 billion light-years away in a well-studied patch of sky called the COSMOS field (for Cosmic Evolution Survey). Each dot is a voracious black hole at the heart of a galaxy, actively feeding off a surrounding disk of material. NASA's Chandra X-ray Observatory and other telescopes have identified many of the black holes in this field, but some are so heavily obscured in gas and dust that NuSTAR's higher-energy X-ray observations are needed to characterize and understand them. Astronomers hope to use NuSTAR to provide new demographics on the numbers, types and distances to black holes that populate our universe.

"This is a hot topic in astronomy," said Francesca Civano of Yale University, New Haven, Conn.  "We want to understand how black holes grew in the past and the degree to which they are obscured."

The ongoing research will help explain how black holes and galaxies grow and interact with each other.

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, N.Y.; NASA's Goddard Space Flight Center, Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center, Rome, Italy.

NuSTAR's mission operations center is at UC Berkeley, with ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

For more information, visit http://www.nasa.gov/nustar and http://www.nustar.caltech.edu/.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Do Black Holes Come in Size Medium?

The magenta spots in this image show two black holes in the spiral galaxy called NGC 1313, or the Topsy Turvy galaxy. Both black holes belong to a class called ultraluminous X-ray sources, or ULXs. The magenta X-ray data come from NASA's Nuclear Spectroscopic Telescopic Array, and are overlaid on a visible image from the Digitized Sky Survey. Image credit: NASA/JPL-Caltech/IRAP.  › Full image and caption

The magenta spots in this image show two black holes in the Circinus galaxy: the supermassive black hole at its heart, and a smaller one closer to the edge that belongs to a class called ultraluminous X-ray sources, or ULXs. The magenta X-ray data come from NASA's Nuclear Spectroscopic Telescopic Array, and are overlaid on a visible/infrared image from the Digitized Sky Survey. Image credit: NASA/JPL-Caltech.  › Full image and caption -  enlarge image

  

Black holes can be petite, with masses only about 10 times that of our sun -- or monstrous, boasting the equivalent in mass up to 10 billion suns. Do black holes also come in size medium? NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, is busy scrutinizing a class of black holes that may fall into the proposed medium-sized category.

"Exactly how intermediate-sized black holes would form remains an open issue," said Dominic Walton of the California Institute of Technology, Pasadena. "Some theories suggest they could form in rich, dense clusters of stars through repeated mergers, but there are a lot of questions left to be answered."

The largest black holes, referred to as supermassive, dominate the hearts of galaxies. The immense gravity of these black holes drags material toward them, forcing the material to heat up and release powerful X-rays. Small black holes dot the rest of the galactic landscape. They form under the crush of collapsing, dying stars bigger than our sun.

Evidence for medium-sized black holes lying somewhere between these two extremes might come from objects called ultraluminous X-ray sources, or ULXs. These are pairs of objects in which a black hole ravenously feeds off a normal star. The feeding process is somewhat similar to what happens around supermassive black holes, but isn't as big and messy. In addition, ULXs are located throughout galaxies, not at the cores.

The bright glow of X-rays coming from ULXs is too great to be the product of typical small black holes. This and other evidence indicates the objects may be intermediate in mass, with 100 to 10,000 times the mass of our sun. Alternatively, an explanation may lie in some kind of exotic phenomenon involving extreme accretion, or "feeding," of a black hole.

NuSTAR is joining with other telescopes to take a closer look at ULXs. It's providing the first look at these objects in focused, high-energy X-rays, helping to get better estimates of their masses and other characteristics.

In a new paper from Walton and colleagues accepted for publication in the Astrophysical Journal, the astronomers report serendipitously finding a ULX that had gone largely unnoticed before. They studied the object, which lies in the Circinus spiral galaxy 13 million light-years away, not only with NuSTAR but also with the European Space Agency's XMM-Newton satellite. Archival data from NASA's Chandra, Swift and Spitzer space telescopes as well as Japan's Suzaku satellite, were also used for further studies. "We went to town on this object, looking at a range of epochs and wavelengths," said Walton.

The results indicate the black hole in question is about 100 times the mass of the sun, putting it right at the border between small and medium black holes.

In another accepted Astrophysical Journal paper, Matteo Bachetti of the Institut de Recherche en Astrophysique et Planétologie and colleagues looked at two ULXs in NGC 1313, a spiral galaxy known as the "Topsy Turvy galaxy," also about 13 million light-years way.

These are among the best-studied ULXs known. A single viewing with NuSTAR showed that the black holes didn't fit with models of medium-size black holes. As a result, the researchers now think both ULXs harbor small, stellar-mass black holes. One of the objects is estimated to be big for its size category, at 70 to 100 solar masses.

"It's possible that these objects are ultraluminous because they are accreting material at a high rate and not because of their size," said Bachetti. "If intermediate-mass black holes are out there, they are doing a good job of hiding from us."

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. 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, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR's mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Catching Black Holes on the Fly

 

An optical color image of galaxies is seen here overlaid with X-ray data (magenta) from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR). Image credit: NASA/JPL-Caltech.  › Full image and caption

NASA's black-hole-hunter spacecraft, the Nuclear Spectroscopic Telescope Array, or NuSTAR, has "bagged" its first 10 supermassive black holes. The mission, which has a mast the length of a school bus, is the first telescope capable of focusing the highest-energy X-ray light into detailed pictures.

The new black-hole finds are the first of hundreds expected from the mission over the next two years. These gargantuan structures -- black holes surrounded by thick disks of gas -- lie at the hearts of distant galaxies between 0.3 and 11.4 billion light-years from Earth.

"We found the black holes serendipitously," explained David Alexander, a NuSTAR team member based in the Department of Physics at Durham University in England and lead author of a new study appearing Aug. 20 in the Astrophysical Journal. "We were looking at known targets and spotted the black holes in the background of the images."

Additional serendipitous finds such as these are expected for the mission. Along with the mission's more targeted surveys of selected patches of sky, the NuSTAR team plans to comb through hundreds of images taken by the telescope with the goal of finding black holes caught in the background.

Once the 10 black holes were identified, the researchers went through previous data taken by NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton satellite, two complementary space telescopes that see lower-energy X-ray light. The scientists found that the objects had been detected before. It wasn't until the NuSTAR observations, however, that they stood out as exceptional, warranting closer inspection.

By combining observations taken across the range of the X-ray spectrum, the astronomers hope to crack unsolved mysteries of black holes. For example, how many of them populate the universe?

"We are getting closer to solving a mystery that began in 1962," said Alexander. "Back then, astronomers had noted a diffuse X-ray glow in the background of our sky but were unsure of its origin. Now, we know that distant supermassive black holes are sources of this light, but we need NuSTAR to help further detect and understand the black hole populations."

This X-ray glow, called the cosmic X-ray background, peaks at the high-energy frequencies that NuSTAR is designed to see, so the mission is key to identifying what's producing the light. NuSTAR can also find the most hidden supermassive black holes, buried by thick walls of gas.

"The highest-energy X-rays can pass right through even significant amounts of dust and gas surrounding the active supermassive black holes," said Fiona Harrison, a study co-author and the mission's principal investigator at the California Institute of Technology, Pasadena.

Data from NASA's Wide-field Infrared Survey Explorer, or WISE, and Spitzer missions also provide missing pieces in the puzzle of black holes by weighing the mass of their host galaxies.

"Our early results show that the more distant supermassive black holes are encased in bigger galaxies," said Daniel Stern, a co-author of the study and the project scientist for NuSTAR at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This is to be expected. Back when the universe was younger, there was a lot more action with bigger galaxies colliding, merging and growing."

Future observations will reveal more about the beastly happenings of black holes, near and far. In addition to hunting remote black holes, NuSTAR is also searching for other exotic objects within our Milky Way galaxy.

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. 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, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR's mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

For more information, visit http://www.nasa.gov/nustar and http://www.nustar.caltech.edu/ .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney.clavin@jpl.nasa.gov

 

Black Hole Naps Amidst Stellar Chaos

The Sculptor galaxy (NGC253) is seen in a new light, in this composite image from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Southern Observatory in Chile. Image credit: NASA/JPL-Caltech/JHU.  › Full image and caption  -  › NuSTAR view only

Nearly a decade ago, NASA's Chandra X-ray Observatory caught signs of what appeared to be a black hole snacking on gas at the middle of the nearby Sculptor galaxy. Now, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), which sees higher-energy X-ray light, has taken a peek and found the black hole asleep. 

"Our results imply that the black hole went dormant in the past 10 years," said Bret Lehmer of the Johns Hopkins University, Baltimore, and NASA's Goddard Space Flight Center, Greenbelt, Md. "Periodic observations with both Chandra and NuSTAR should tell us unambiguously if the black hole wakes up again. If this happens in the next few years, we hope to be watching." Lehmer is lead author of a new study detailing the findings in the Astrophysical Journal. 

The slumbering black hole is about 5 million times the mass of our sun. It lies at the center of the Sculptor galaxy, also known as NGC 253, a so-called starburst galaxy actively giving birth to new stars. At 13 million light-years away, this is one of the closest starbursts to our own galaxy, the Milky Way. 

The Milky Way is all around more quiet than the Sculptor galaxy. It makes far fewer new stars, and its behemoth black hole, about 4 million times the mass of our sun, is also snoozing. 

"Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant," said co-author Ann Hornschemeier of Goddard. "NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it." 

The findings are teaching astronomers how galaxies grow over time. Nearly all galaxies are suspected to harbor supermassive black holes at their hearts. In the most massive of these, the black holes are thought to grow at the same rate that new stars form, until blasting radiation from the black holes ultimately shuts down star formation. In the case of the Sculptor galaxy, astronomers do not know if star formation is winding down or ramping up. 

"Black hole growth and star formation often go hand-in-hand in distant galaxies," said Daniel Stern, a co-author and NuSTAR project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It's a bit surprising as to what's going on here, but we've got two powerful complementary X-ray telescopes on the case." 

Chandra first observed signs of what appeared to be a feeding supermassive black hole at the heart of the Sculptor galaxy in 2003. As material spirals into a black hole, it heats up to tens of millions of degrees and glows in X-ray light that telescopes like Chandra and NuSTAR can see. 

Then, in September and November of 2012, Chandra and NuSTAR observed the same region simultaneously. The NuSTAR observations -- the first-ever to detect focused, high-energy X-ray light from the region -- allowed the researchers to say conclusively that the black hole is not accreting material. NuSTAR launched into space in June of 2012. 

In other words, the black hole seems to have fallen asleep. Another possibility is that the black hole was not actually awake 10 years ago, and Chandra observed a different source of X-rays. Future observations with both telescopes may solve the puzzle. 

"The combination of coordinated Chandra and NuSTAR observations is extremely powerful for answering questions like this," said Lou Kaluzienski, NuSTAR Program Scientist at NASA Headquarters in Washington. "Now, we can get all sides of the story." 

The observations also revealed a smaller, flaring object that the researchers were able to identify as an "ultraluminous X-ray source," or ULX. ULXs are black holes feeding off material from a partner star. They shine more brightly than typical stellar-mass black holes generated from dying stars, but are fainter and more randomly distributed than the supermassive black holes at the centers of massive galaxies. Astronomers are still working to understand the size, origins and physics of ULXs. 

"These stellar-mass black holes are bumping along near the center of this galaxy," said Hornschemeier. "They tend to be more numerous in areas where there is more star-formation activity." 

If and when the Sculptor's slumbering giant does wake up in the next few years amidst all the commotion, NuSTAR and Chandra will monitor the situation. The team plans to check back on the system periodically.

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. 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, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center. 

NuSTAR's mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. 

For more information, visit: http://www.nasa.gov/nustar and http://www.nustar.caltech.edu/ . Follow the mission on Twitter via http://www.twitter.com/NASANuSTAR . 

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Speedy Black Hole Holds Galaxy's History

 Rapidly rotating black hole accreting matter

ESA’s XMM-Newton and NASA’s NuSTAR have detected a rapidly rotating supermassive black hole in the heart of spiral galaxy NGC 1365. The rate at which a black hole spins encodes the history of its formation. An extremely rapid rotation could result from either a steady and uniform flow of matter spiralling in via an accretion disc (as shown in this artist impression) or as a result of the merger of two galaxies and their smaller black holes.

Also depicted in this image is an outflowing jet of energetic particles, believed to be powered by the black hole’s spin. The regions near black holes contain compact sources of high energy X-ray radiation thought, in some scenarios, to originate from the base of these jets. The nature of the X-ray emission enables astronomers to see how fast matter is swirling in the inner region of the disc, and ultimately to measure the black hole's spin rate. Download Hi-Res (955.29 kB)

A rapidly rotating supermassive black hole has been found in the heart of a spiral galaxy by ESA’s XMM-Newton and NASA’s NuSTAR space observatories, opening a new window into how galaxies grow.

Supermassive black holes are thought to lurk in the centre of almost all large galaxies, and scientists believe that the evolution of a galaxy is inextricably linked with the evolution of its black hole. 

How fast a black hole spins is thought to reflect the history of its formation. In this picture, a black hole that grows steadily, fed by a uniform flow of matter spiralling in, should end up spinning rapidly. Rapid rotation could also be the result of two smaller black holes merging.  

On the other hand, a black hole buffeted by small clumps of material hitting from all directions will end up rotating relatively slowly. 

These scenarios mirror the formation of the galaxy itself, since a fraction of all the matter drawn into the galaxy finds its way into the black hole. Because of this, astronomers are keen to measure the spin rates of black holes in the hearts of galaxies. 

One way of doing so is to observe X-rays emitted just outside the ‘event horizon’, the boundary surrounding a black hole beyond which nothing, including light, can escape. 

In particular, hot iron atoms produce a strong signature of X-rays at a specific energy, which is smeared out by the rotation of the black hole. The nature of this smearing can then be used to infer the spin rate. 

Using this technique, previous observations have suggested there are extremely rapidly spinning black holes in some galaxies. However, confirming the spin rate has been very difficult, because the X-ray spectrum can also be smeared out by absorbing clouds of gas lying close to the disc. Until now, telling the two scenarios apart has been impossible. 

For roughly 36 hours in July 2012, ESA’s XMM-Newton and NASA’s NuSTAR – the Nuclear Spectroscopic Telescope Array – simultaneously observed the spiral galaxy NGC 1365. XMM-Newton captured the lower energy X-rays, NuSTAR the higher energy data. 

The combined data proved to be key to unlocking the puzzle. A spinning black hole model makes a clear prediction for the ratio of high-energy to low-energy X-rays. The same is true for an absorbing cloud of gas. 

But importantly, the predictions are different and the new data agree only with a rapidly spinning black hole. This suggests that the galaxy has grown steadily with time, with material streaming uniformly into the central black hole. 

However, astronomers cannot yet rule out a single large event where two galaxies and their black holes subsequently merged, producing a sudden acceleration of the resulting supermassive black hole. 

“But we can completely rule out the absorption model,” says Guido Risaliti, INAF – Osservatorio Astrofisico di Arcetri, Italy, who led the investigation. 

“Now that we know how to measure black hole spin rates for certain, we can more confidently use them to infer the evolution of their host galaxies.”

Measuring black hole spins also provides a new way to test general relativity. Published in 1915, general relativity is Albert Einstein’s description of gravity. It predicts effects that are most easily seen in extremely strong gravitational fields, such as those found near black holes, and NGC 1365’s black hole is spinning almost as fast as Einstein's theory of gravity will allow. 

“Both physics and astrophysics benefit from this result,’ says Dr Risaliti, who is already applying the X-ray measurement technique to different galaxies. 

“The result is a great example of the synergy that can be achieved when complementary space missions are used together. It would have been impossible to achieve this work without the two spacecraft working in tandem,” says Norbert Schartel, ESA XMM-Newton project scientist.

 

Notes for Editors

 

“A rapidly spinning supermassive black hole at the centre of NGC 1365” by G. Risaliti et al. is published in Nature 28 February 2013; doi:10.1038/nature11938.

The European Space Agency's X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. It is the biggest scientific satellite to have been built in Europe and uses over 170 wafer-thin cylindrical mirrors spread over three high throughput X-ray telescopes. Its mirrors are among the most powerful ever developed. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects. The scientific community can apply for observing time on XMM-Newton on a competitive basis. 

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. 

For further information, please contact:
 
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int

Guido Risaliti
INAF–Osservatorio Astrofisico di Arcetri
Tel: +39 055 2752286
Email: risaliti@arcetri.astro.it

Norbert Schartel
ESA XMM-Newton Project Scientist
Tel: +34 91 8131 184
Email: norbert.schartel@esa.int

NASA's NuSTAR Catches Black Holes in Galaxy Web

   

This new view of spiral galaxy IC 342, also known as Caldwell 5, includes data from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. High-energy X-ray data from NuSTAR have been translated to the color magenta, and superimposed on a visible-light view highlighting the galaxy and its star-studded arms. NuSTAR is the first orbiting telescope to take focused pictures of the cosmos in high-energy X-ray light; previous observations of this same galaxy taken at similar wavelengths blurred the entire object into one pixel. Image credit: NASA/JPL-Caltech/DSS . › Full image and caption

 

This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. Blue indicates the highest energy X-ray light, where NuSTAR has made the first resolved image ever of this source. Red and green show the lower end of NuSTAR's energy range, which overlaps with NASA's high-resolution Chandra X-ray Observatory. Image credit: NASA/JPL-Caltech/DSS . › Full image and caption   - enlarge image

PASADENA, Calif. - NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, set its X-ray eyes on a spiral galaxy and caught the brilliant glow of two black holes lurking inside.

The new image is being released Monday along with NuSTAR's view of the supernova remnant Cassiopeia A, at the American Astronomical Society meeting in Long Beach, Calif.

"These new images showcase why NuSTAR is giving us an unprecedented look at the cosmos," said Lou Kaluzienski, NuSTAR program scientist at NASA headquarters in Washington. "With NuSTAR's greater sensitivity and imaging capability, we're getting a wealth of new information on a wide array of cosmic phenomena in the high-energy X-ray portion of the electromagnetic spectrum."

Launched last June, NuSTAR is the first orbiting telescope with the ability to focus high-energy X-ray light. It can view objects in considerably greater detail than previous missions operating at similar wavelengths. Since launch, the NuSTAR team has been fine-tuning the telescope, which includes a mast the length of a school bus connecting the mirrors and detectors.

The mission has looked at a range of extreme, high-energy objects already, including black holes near and far, and the incredibly dense cores of dead stars. In addition, NuSTAR has begun black hole searches in the inner region of the Milky Way galaxy and in distant galaxies in the universe.

Among the telescope's targets is the spiral galaxy IC342, also known as Caldwell 5, featured in one of the two new images. This galaxy lies 7 million light-years away in the constellation Camelopardalis (the Giraffe). Previous X-ray observations of the galaxy from NASA's Chandra X-ray Observatory revealed the presence of two blinding black holes, called ultraluminous X-ray sources (ULXs).

How ULXs can shine so brilliantly is an ongoing mystery in astronomy. While these black holes are not as powerful as the supermassive black hole at the hearts of galaxies, they are more than 10 times brighter than the stellar-mass black holes peppered among the stars in our own galaxy. Astronomers think ULXs could be less common intermediate-mass black holes, with a few thousand times the mass of our sun, or smaller stellar-mass black holes in an unusually bright state. A third possibility is that these black holes don't fit neatly into either category.

"High-energy X-rays hold a key to unlocking the mystery surrounding these objects," said Fiona Harrison, NuSTAR principal investigator at the California Institute of Technology in Pasadena. "Whether they are massive black holes, or there is new physics in how they feed, the answer is going to be fascinating."

In the image, the two bright spots that appear entangled in the arms of the IC342 galaxy are the black holes. High-energy X-ray light has been translated into the color magenta, while the galaxy itself is shown in visible light.

"Before NuSTAR, high-energy X-ray pictures of this galaxy and the two black holes would be so fuzzy that everything would appear as one pixel," said Harrison.

The second image features the well-known, historical supernova remnant Cassiopeia A, located 11,000 light-years away in the constellation Cassiopeia. The color blue indicates the highest-energy X-ray light seen by NuSTAR, while red and green signify the lower end of NuSTAR's energy range. The blue region is where the shock wave from the supernova blast is slamming into material surrounding it, accelerating particles to nearly the speed of light. As the particles speed up, they give off a type of light known as synchrotron radiation. NuSTAR will be able to determine for the first time how energetic the particles are, and address the mystery of what causes them to reach such great speeds.

"Cas A is the poster child for studying how massive stars explode and also provides us a clue to the origin of the high-energy particles, or cosmic rays, that we see here on Earth," said Brian Grefenstette of Caltech, a lead researcher on the observations. "With NuSTAR, we can study where, as well as how, particles are accelerated to such ultra-relativistic energies in the remnant left behind by the supernova explosion."

For more information about NuSTAR and to view the new images, visit: http://www.nasa.gov/nustar .

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena for NASA's Science Mission Directorate in Washington. Orbital Sciences Corporation of Dulles, Va., built the spacecraft. Its instrument was built by a consortium including Caltech; JPL; the University of California (UC) Berkeley; Columbia University; NASA's Goddard Space Flight Center in Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory in Livermore, Calif.; and ATK Aerospace Systems of Goleta, Calif. NuSTAR's mission operations center is at UC Berkeley, with the Italian Space Agency providing an equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University in Rohnert Park, Calif. Goddard manages NASA's Explorer Program. Caltech manages JPL for NASA.

You can follow JPL News on Facebook at: http://www.facebook.com/nasajpl and on Twitter at: http://www.twitter.com/nasajpl . Caltech manages JPL for NASA.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

J.D. Harrington 202-358-5241
NASA Headquarters, Washington
j.d.harrington@nasa.gov

The Diner at the Center of the Galaxy

A new ScienceCast video explores the Milky Way's central black hole
Play it

An artist's concept of NuSTAR in Earth orbit. More

"We got lucky and captured an outburst from the black hole during our [first] observing campaign," says Fiona Harrison, the mission's principal investigator at the California Institute of Technology.

NuSTAR is an orbiting observatory designed to take pictures of violent, high-energy phenomena in the universe.  Launched on June 13, 2012, it is the only telescope capable of producing focused images of the highest-energy X-rays produced by dying stars and ravenous black holes.

"It's like putting on a new pair of glasses and seeing aspects of the world around us clearly for the first time," says Harrison.  NuSTAR's first light image of Cygnus X-1, a black hole in our galaxy that is siphoning gas off a giant-star companion, shows what she's talking about: click here

NuSTAR's sharp vision allowed it to pinpoint a burst of hard X-rays coming from the galactic center during an observing campaign in July.  Lower-energy X-ray observations by NASA's Chandra X-ray Observatory and infrared data from the Keck telescope in Hawaii confirmed the outburst.  The Milky Way's black hole had just swallowed ... something.

Black hole snacks are a violent process in which the "meal" is ripped apart by powerful tides and heated to  millions of degrees as it slides down the gullet of the gravitational singularity.   In this case, NuSTAR picked up X-rays emitted by matter being heated up to about 100 million degrees Celsius.

The observation raises hopes that astronomers will be able to solve a long-standing mystery:  Why is the Milky Way's supermassive black hole such a picky eater?

Compared to giant black holes at the centers of other galaxies, the Milky Way's is relatively quiet. More active black holes tend to gobble up matter in prodigious quantities. Ours, on the other hand, is thought only to nibble or not eat at all.

Asteroids could be a primary food source. One model holds that trillions of asteroids surround the Milky Way's core. Astronomers using the Chandra X-ray Observatory have indeed detected flares consistent with asteroids 10 km wide or larger falling into the black hole.  These space rocks would be about the same size as the asteroid that wiped out the dinosaurs on Earth 65 million years ago.  Smaller space rocks might be falling in, too, but their flares would be too weak for Chandra to detect.

NuSTAR brings something new to the problem. With its unprecedented ability to detect and make focused images of X-ray flares, the telescope will almost certainly help astronomers understand what's happening deep in the core of our galaxy.  The monster's menu might soon be revealed.

For more information about NuSTAR and its focused observations of black holes, visit the mission's home page at nustar.caltech.edu.

Author: Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit: Science@NASA

NASA's NuSTAR Spots Flare From Milky Way's Black Hole

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light. Image credit: NASA/JPL-Caltech.  Full image and caption

These are the first, focused high-energy X-ray views of the area surrounding the supermassive black hole, called Sagittarius A*, at the center of our galaxy. Image credit: NASA/JPL-Caltech.

Full image and caption  -  enlarge image

PASADENA, Calif. - NASA's newest set of X-ray eyes in the sky, the Nuclear Spectroscopic Telescope Array (NuSTAR), has caught its first look at the giant black hole parked at the center of our galaxy. The observations show the typically mild-mannered black hole during the middle of a flare-up. 

"We got lucky to have captured an outburst from the black hole during our observing campaign," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology (Caltech) in Pasadena. "These data will help us better understand the gentle giant at the heart of our galaxy and why it sometimes flares up for a few hours and then returns to slumber." 

The new images can be seen by visiting: http://www.nasa.gov/nustar .

NuSTAR, launched June 13, is the only telescope capable of producing focused images of the highest-energy X-rays. For two days in July, the telescope teamed up with other observatories to observe Sagittarius A* (pronounced Sagittarius A-star and abbreviated Sgr A*), the name astronomers give to a compact radio source at the center of the Milky Way. Observations show a massive black hole lies at this location. Participating telescopes included NASA's Chandra X-ray Observatory, which sees lower-energy X-ray light; and the W.M. Keck Observatory atop Mauna Kea in Hawaii, which took infrared images. 

Compared to giant black holes at the centers of other galaxies, Sgr A* is relatively quiet. Active black holes tend to gobble up stars and other fuel around them. Sgr A* is thought only to nibble or not eat at all, a process that is not fully understood. When black holes consume fuel -- whether a star, a gas cloud or, as recent Chandra observations have suggested, even an asteroid -- they erupt with extra energy. 

In the case of NuSTAR, its state-of-the-art telescope is picking up X-rays emitted by consumed matter being heated up to about 180 million degrees Fahrenheit (100 million degrees Celsius) and originating from regions where particles are boosted very close to the speed of light. Astronomers say these NuSTAR data, when combined with the simultaneous observations taken at other wavelengths, will help them better understand the physics of how black holes snack and grow in size. 

"Astronomers have long speculated that the black hole's snacking should produce copious hard X-rays, but NuSTAR is the first telescope with sufficient sensitivity to actually detect them," said NuSTAR team member Chuck Hailey of Columbia University in New York City. 

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena for NASA's Science Mission Directorate in Washington. Orbital Sciences Corporation of Dulles, Va., built the spacecraft. Its instrument was built by a consortium including Caltech; JPL; the University of California (UC) Berkeley; Columbia University; NASA's Goddard Space Flight Center in Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory in Livermore, Calif.; and ATK Aerospace Systems of Goleta, Calif. 

NuSTAR's mission operations center is at UC Berkeley, with the Italian Space Agency providing an equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University in Rohnert Park, Calif. Goddard manages NASA's Explorer Program. Caltech manages JPL for NASA. 

For information about NASA and agency programs, visit: http://www.nasa.gov .

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov 

J.D. Harrington 202-358-5241
NASA Headquarters, Washington
j.d.harrington@nasa.gov