NuSTAR discovers impossibly bright dead star - First ultraluminous pulsar

High-energy X-rays streaming from a rare and mighty pulsar (magenta), the brightest found to date, can be seen in this new image combining multi-wavelength data from three telescopes. 

The bulk of a galaxy called Messier 82 (M82), or the 'Cigar galaxy,' is seen in visible-light data captured by the National Optical Astronomy Observatory's 2.1-meter telescope at Kitt Peak in Arizona. 

Starlight is white, and lanes of dust appear brown. Low-energy X-ray data from NASA's Chandra X-ray Observatory are colored blue, and higher-energy X-ray data from NuSTAR are pink. 

Credit: NASA/JPL-Caltech/SAO/NOAO

Astronomers working with NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), led by Caltech's Fiona Harrison, have found a pulsating dead star beaming with the energy of about 10 million suns.

The object, previously thought to be a black hole because it is so powerful, is in fact a pulsar, the incredibly dense rotating remains of a star.

"This compact little stellar remnant is a real powerhouse. We've never seen anything quite like it," says Harrison, NuSTAR's principal investigator and the Benjamin M. Rosen Professor of Physics at Caltech.

"We all thought an object with that much energy had to be a black hole."

Dom Walton, a postdoctoral scholar at Caltech who works with NuSTAR data, says that with its extreme energy, this pulsar takes the top prize in the weirdness category. Pulsars are typically between one and two times the mass of the sun.

This new pulsar presumably falls in that same range but shines about 100 times brighter than theory suggests something of its mass should be able to.

"We've never seen a pulsar even close to being this bright," Walton says. "Honestly, we don't know how this happens, and theorists will be chewing on it for a long time."

Besides being weird, the finding will help scientists better understand a class of very bright X-ray sources, called ultraluminous X-ray sources (ULXs).

Harrison, Walton, and their colleagues describe NuSTAR's detection of this first ultraluminous pulsar in a paper that appears in the current issue of Nature.

"This was certainly an unexpected discovery," says Harrison. "In fact, we were looking for something else entirely when we found this."



This animation shows a neutron star, the core of a star that exploded in a massive supernova. 

This particular neutron star is known as a pulsar because it sends out rotating beams of X-rays that sweep past Earth like lighthouse beacons. 

Credit: NASA/JPL-Caltech

Earlier this year, astronomers in London detected a spectacular, once-in-a-century supernova (dubbed SN2014J) in a relatively nearby galaxy known as Messier 82 (M82), or the Cigar Galaxy, 12 million light-years away.

Because of the rarity of that event, telescopes around the world and in space adjusted their gaze to study the aftermath of the explosion in detail.

Besides the supernova, M82 harbours a number of other ULXs. When Matteo Bachetti of the Université de Toulouse in France, the lead author of this new paper, took a closer look at these ULXs in NuSTAR's data, he discovered that something in the galaxy was pulsing, or flashing light.

"That was a big surprise," Harrison says. "For decades everybody has thought these ultraluminous X-ray sources had to be black holes, but black holes don't have a way to create this pulsing."

More information: An Ultraluminous X-ray Source Powered by An Accreting Neutron Star, Nature, dx.doi.org/10.1038/nature13791189

NASA NuSTAR: Rare blurring of Black Hole X-Ray light

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

NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has captured 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 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 spiraling inward," said Michael Parker of the Institute of Astronomy in Cambridge, United Kingdom, lead author of a new paper on the findings appearing in the 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 centers 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.

This plot of data captured by NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), shows X-ray light streaming from regions near a supermassive black hole known as Markarian 335. 

Credit: NASA

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 is still in this close configuration, months after it moved.

Researchers don't know whether and when the corona will shift back. What's 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."

More information: "Black hole spin and size of the X-ray-emitting region(s) in the Seyfert 1.5 galaxy ESO 362-G18," B. Agís-González, G. Miniutti, E. Kara, A. C. Fabian, M. Sanfrutos, G. Risaliti, S. Bianchi, N. L. Strotjohann, R. D. Saxton and M. L. Parker, Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press: mnras.oxfordjournals.org/content/443/4/2862

NASA NuSTAR: Fiona Harrison speaks about the mission - Video

The Nuclear Spectroscopic Telescope Array (NuSTAR), sees the high-energy X-rays emitted by the densest, hottest regions of the universe.

The brainchild of Fiona Harrison, Caltech's Benjamin M. Rosen Professor of Physics and Astronomy and NuSTAR's principal investigator, the phone-booth-sized NuSTAR was launched from beneath an airplane's wing, unfolding to the length of a school bus once in orbit.

Professor Harrison will describe NuSTAR's unlikely journey and share some of its remarkable results at 8:00 p.m. on Wednesday, December 4, in Caltech's Beckman Auditorium. Admission is free.



Q: What's "new" about NuSTAR?

NuSTAR is the first focusing high-energy X-ray telescope. X-rays can be focused by reflection, but they're so penetrating that they only reflect at very glancing angles—sort of like skipping a stone off the surface of a lake.

But most of the X-rays don't interact even then, so you use "nested optics," which you can think of as a set of cones nested inside one another like Russian dolls.

Each cone intercepts some of the X-ray beam. The higher the energy, the more glancing the reflecting angle is, and the more cones you need.

Other focusing telescopes, such as NASA's Chandra X-ray Observatory and the European Space Agency's X-ray Multi-Mirror Mission, observe X-rays with energies below about 10 kilo-electronvolts. NuSTAR can see up to 79 kilo-electronvolts.

Chandra has four nested mirrors, each about an inch thick and set at about a one-degree angle; NuSTAR has 133 mirrors as thin as my fingernail and almost parallel to the incoming light.

We developed the detector here at Caltech. It's a digital camera, but made out of a special material that stops the high-energy X-rays that would have gone straight through previous X-ray imaging detectors.

NuSTAR is hundreds of times more sensitive, and its images are 10 times crisper than its nonfocusing predecessors, which basically worked like the pinhole camera you may have used to watch a solar eclipse.

So we're able to observe the universe to much greater depth and in much greater detail than has previously been possible.

Q: What does NuSTAR see that we wouldn't see at other wavelengths?

A whole variety of things. Medical X-rays are about 60 kilo-electronvolts, which is in the band that we observe.

They penetrate the skin but stop in the bones, casting a shadow that shows up on the film. Similarly, we can look into the hearts of galaxies with high-energy X-rays, which penetrate the clouds of dust and gas where low-energy X-rays would be absorbed.

We can see supermassive black holes, or rather the X-rays emitted by the very hot stuff falling into them. We can see neutron stars, which are the collapsed cores of burned-out stars so dense that a teaspoon of neutron star would weigh more than all of humanity. We can see the remnants of dead, exploded stars.
Q: What is your role in all this?

We built a pinhole-camera-type X-ray telescope as part of my PhD work at Berkeley in the early '90s, but we needed something much more sensitive to do what we really wanted to do.

So we came down to Caltech, and we began developing NuSTAR's technology for a balloon experiment called the High-Energy Focusing Telescope, or HEFT. HEFT flew in 2005 and it was so successful that we submitted a proposal to NASA's Small Explorer program to build a space version.

As the principal investigator, I was responsible for putting the team together that proposed NuSTAR to NASA, and for overseeing the construction and launch.

Now I lead the science team, which decides what to look at and analyzes all the data. Our primary mission ends in 2014, so right now I'm starting to write a proposal to extend the mission for another two years as a guest-investigator program open to anyone anywhere in the world.

I hope NuSTAR keeps me busy for another 10 years or more. There are no expendables such as cryogenic coolant, so it's a matter of how long the orbit lasts.

We do experience atmospheric drag, so NuSTAR will eventually reenter and burn up. Either that, or something will break. As a small, inexpensive mission, we don't have redundant systems. If something breaks, there's no backup to switch over to.

NASA NuSTAR: Space Telescope Discovers 10 Monster Black Holes

This optical colour image of galaxies is seen overlaidwith X-ray data (magenta) from NASA's black hole-hunting NuSTAR space telescope. 

The arrow points to magenta blobs indicating giant, supermassive black holes discovered by the space telescope. 

Credit: NASA/JPL-Caltech`

A powerful NASA space telescope has found not one, but 10 monster black holes lurking in the hearts of distant galaxies — the first major finds for the X-ray space observatory, scientists say.

The discoveries, which scientists say occurred "serendipitously," were made as astronomers reviewed images from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), an X-ray space telescope designed specifically to hunt black holes.

"We were looking at known targets and spotted the black holes in the background of the images," David Alexander, a professor with Durham University's physics department, said in a statement.

Then the team confirmed what they saw with observations from NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton satellite, which also can look at low-energy light.

The 10 black holes discovered are just the beginning of hundreds of expected finds, the scientists added. With every supermassive black hole catalogued, scientists are hoping to better understand the population.

Surrounded by galaxies
According to NASA, discovering the supermassive black holes were a key piece of a puzzle first uncovered in 1962. Astronomers found a glow of X-rays in the background of the universe, but didn't know where the glow came from.

Today, scientists know the glow (also called the cosmic X-ray background) comes from very distant supermassive black holes, some of which are as large as 17 billion times the mass of the sun. But how these black holes form is still under investigation.

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

While NuSTAR can detect these big black holes, other measurements (such as mass) come from agency observatories including the Wide-field Infrared Survey Explorer (WISE) and Spitzer Space Telescope.

The research appeared Aug. 20 in the Astrophysical Journal.

NASA NuSTAR: Collected Data on First 10 Black Hole

NASA says its black-hole-hunting NuSTAR spacecraft has "bagged" its first 10 supermassive black holes, the first of hundreds expected in a 2-year mission.

The Nuclear Spectroscopic Telescope Array, sporting 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 agency's Jet Propulsion Laboratory in Pasadena, Calif., said Thursday.

Supermassive black holes surrounded by thick disks of gas lie at the hearts of distant galaxies between 0.3 billion and 11.4 billion light-years from Earth, project scientists said.

The first NuSTAR findings were unexpected but welcome, they said.

David Alexander

"We found the black holes serendipitously," David Alexander, a NuSTAR team member in the Department of Physics at Durham University in UK, said.

"We were looking at known targets and spotted the black holes in the background of the images."

Astronomers said they hope X-ray surveys by NuSTAR can help crack unsolved mysteries surrounding black holes, including how many of them populate the universe.

"We are getting closer to solving a mystery that began in 1962," Alexander said.

"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."

NASA NuSTAR delivers the X-ray goods

Artist's concept of NuSTAR on orbit. NuSTAR has a 10-m (30') mast that deploys after launch to separate the optics modules (right) from the detectors in the focal plane (left). 

Credit: NASA/JPL-Caltech

NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), is giving the wider astronomical community a first look at its unique X-ray images of the cosmos.

The first batch of data from the black-hole hunting telescope was publicly available on Aug. 29, via NASA's High Energy Astrophysics Science Archive Research Center, (HEASARC).

Fiona Harrison

"We are pleased to present the world with NuSTAR's first look at the sky in high-energy X-rays with a true focusing telescope," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology (Caltech), Pasadena.

The images, taken from July to August 2012, shortly after the spacecraft launched, comprise an assortment of extreme objects, including black holes near and far.

The more distant black holes are some of the most luminous objects in the universe, radiating X-rays as they ferociously consume surrounding gas.

One type of black hole in the new batch of data is a blazar, which is an active, supermassive black hole pointing a jet toward Earth.

Systems known as X-ray binaries, in which a compact object such as a neutron star or black hole feeds off a stellar companion, are also in the mix, along with the remnants of stellar blasts called supernovas.

The data set only contains complete observations. Data will be released at a later date for those targets still being observed.

"Astronomers can use these data to better understand the capabilities of NuSTAR and design future observing proposals. The first opportunity will be this fall, for joint observations with XMM-Newton," said Karl Forster of Caltech, who is leading the effort to package the data for the public.

The European Space Agency's XMM-Newton X-ray telescope, like NASA's Chandra X-ray Observatory, complements NuSTAR.

While XMM-Newton and Chandra see lower-energy X-ray light, NuSTAR is the first telescope capable of focusing high-energy X-ray light, allowing for more detailed images than were possible before.

Astronomers can compare data sets from different missions using HEASARC, which gives them a broader understanding of an object of interest.

NuSTAR's high-energy observations help scientists bridge a gap that existed previously in X-ray astronomy, and will lead to new revelations about the bizarre and energetic side of our universe.

Other NASA missions with data available via HEASARC include Chandra, Fermi, Swift, Cosmic Background Explorer (COBE), Wilkinson Microwave Anisotropy Probe (WMAP) and many more.

NASA NuSTAR: Black Hole Dormant Amidst Stellar Chaos

The Sculptor galaxy 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. 

Credit: NASA/JPL-Caltech/JHU

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.

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 .

NASA NuSTAR X-Ray Data analysis of Spiral galaxy

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.

The two magenta spots are blazing black holes first detected at lower-energy X-ray wavelengths by NASA's Chandra X-ray Observatory.

With NuSTAR's complementary data, astronomers can start to home in on the black holes' mysterious properties.

The black holes appear much brighter than typical stellar-mass black holes, such as those that pepper our own galaxy, yet they cannot be supermassive black holes or they would have sunk to the galaxy’s center.

Instead, they may be intermediate in mass, or there may be something else going on to explain their extremely energetic state. NuSTAR will help solve this puzzle.

IC 342 lies 7 million light-years away in the Camelopardalis constellation. The outer edges of the galaxy cannot be seen in this view.

This image shows NuSTAR X-ray data taken at 10 to 35 kiloelectron volts.

The visible-light image is from the Digitized Sky Survey.

› NuSTAR data only

Image credit: NASA/JPL-Caltech/DSS