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GALLERY: Black holes galore

AN ASSORTMENT OF BLACK HOLES lights up a new image from NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR. Although the coloured blobs might not look like much, every one of them is a black hole located inside the hearts of a galaxy.

The different colours represent different energies of X-ray light. The red, yellow and green colours represent black holes seen previously by NASA’s Chandra X-ray Observatory (with red denoting the lowest-energy X-ray light). The colour blue shows black holes recently detected by NuSTAR, which is uniquely designed to detect the highest-energy X-ray light.

Image showing X-ray emission from black holes

Every one of the blobs you can see here, represents the location of a black hole. Although black holes cannot be directly seen, the X-ray light given off by hot gas in the vicinity can – and that’s what we see here; X-ray emission detected by the Chandra and NuSTAR space observatories.

The black holes in this picture are between about 3 to 10 billion light-years away.

The X-rays aren’t coming from the black holes themselves, since nothing can escape the gravitational grip of a black hole. Rather, they are coming from hot gas in the vicinity of the black holes.

Why do some black holes produce more high-energy X-ray light than others? Astronomers say this is because the black holes are more actively feeding off surrounding clouds of dust and gas – a process which heats up the gas and makes it emit X-rays.

The image shows an area, called the COSMOS field, that has been studied in great detail by many telescopes (COSMOS stands for Cosmic Evolution Survey). Red and green represent X-ray light seen by Chandra. Blue is for the kind of X-ray light that can only be seen by NuSTAR.

Adapted from information issued by NASA / JPL-Caltech / Yale University.

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Inside-out exploding star

Cassiopeia A: artist's impression of the precursor star and real X-ray image of the remnant

Before and after the explosion. Colour coded elements in artist's impression of the star's core match up with real observations of Cassiopeia A. Iron, shown in blue, has somehow gone from being in the middle of the star to the outskirts of the supernova remnant.

IN THE NORTHERN CONSTELLATION Cassiopeia lies a famous supernova remnant, a gas cloud that represents the shattered remains of a once-titanic star.

Known as Cassiopeia A, it is hard to see at normal visible light wavelengths but shines strongly at radio and X-ray wavelengths.

A supernova of this kind occurs when a massive star runs out of nuclear fuel and can no longer produce energy. Without an outflow of energy to keep the star “inflated”, it’s huge mass crushes inwards … producing an implosion followed by an explosion that tears the star apart.

In the millions of years leading up to the explosion, the star’s innards become layered with different elements as a result of different nuclear fusion processes. In the core there is a globe of iron. Surrounding that are layers of sulphur, silicon, magnesium, neon and oxygen.

It would seem to make sense that when the star explodes, the outer layers would end up on the outskirts of the resulting gas cloud, with the iron concentrated toward the middle.

But by compiling a staggering one million seconds worth of X-ray observations by satellite telescopes, astronomers have found that this is not the case for Cassiopeia A.

The observations show that the distribution of sulphur, silicon, magnesium and neon is about as expected. But the iron is spread around the outer part of the supernova remnant, and there’s none in the middle.

The astronomers think there must have been some sort of “instability” in the supernova explosion process, which turned the star inside out.

Story by Jonathan Nally. Images courtesy (illustration) NASA / CXC / M.Weiss; (X-ray) NASA / CXC / GSFC / U.Hwang & J.Laming.

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Take a tour of the Crab Nebula

THE CRAB NEBULA IS ONE OF THE BRIGHTEST sources of high-energy radiation in the sky. Little wonder—it’s the expanding remains of an exploded star, a supernova seen in 1054.

Scientists have used virtually every telescope at their disposal, including NASA’s Chandra X-ray Observatory, to study the Crab.

The supernova left behind a magnetised neutron star—a pulsar. It’s about the size of Washington DC, but it spins 30 times per second. Each rotation sweeps a lighthouse-like beam past us, creating a pulse of electromagnetic energy detectable across the spectrum.

The pulsar in the Crab Nebula is among the brightest sources of high-energy gamma rays. Recently, NASA’s Fermi Gamma Ray Observatory and Italy’s AGILE Satellite detected strong gamma-ray flares from the Crab, including a series of “superflares” in April 2011.

To help pinpoint the location of these flares, astronomers enlisted Chandra space telescope.

With its keen X-ray eyes, Chandra saw lots of activity, but none of it seems correlated with the superflare. This hints that whatever is causing the flares is happening with about a third of a light-year from the pulsar. And rapid changes in the rise and fall of gamma rays imply that the emission region is very small, comparable in size to our Solar System.

The Chandra observations will likely help scientists to home in on an explanation of the gamma-ray flares one day.

Even after a thousand years, the heart of this shattered star still offers scientists glimpses of staggering energies and cutting edge science.

Adapted from information issued by Harvard-Smithsonian Centre for Astrophysics. Still image courtesy (X-ray) NASA / CXC / SAO / F.Seward, (optical) NASA / ESA / ASU / J.Hester & A.Loll, (infrared) NASA / JPL-Caltech / Univ. Minn. / R.Gehrz.

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Space spin-offs – better cancer therapy

Artist's impression of a black hole

Safer, lower-dose medical scans are on their way, thanks to astronomers' studies of radiation from astronomical bodies such as black holes.

ASTRONOMERS ARE WORKING with medical physicists and radiation oncologists to develop a potential new radiation treatment—one that is intended to be tougher on tumours, but gentler on healthy tissue.

In studying how chemical elements emit and absorb radiation inside stars and around black holes, the astronomers discovered that heavy metals such as iron emit low-energy electrons when exposed to X-rays at specific energies.

Their discovery raises the possibility that implants made from certain heavy elements could enable doctors to obliterate tumours with low-energy electrons, while exposing healthy tissue to much less radiation than is possible today.  Similar implants could enhance medical diagnostic imaging.

Last month, at the International Symposium on Molecular Spectroscopy, Ohio State University senior research scientist Sultana Nahar announced the team’s computer simulations of the elements gold and platinum, and the design of a prototype device that generates X-rays at key frequencies.

Their simulations suggest that hitting a single gold or platinum atom with a small dose of X-rays at a narrow range of frequencies—equal to roughly one tenth of the broad spectrum of X-ray radiation frequencies—produces a flood of more than 20 low-energy electrons.

“As astronomers, we apply basic physics and chemistry to understand what’s happening in stars. We’re very excited to apply the same knowledge to potentially treat cancer,” Nahar said.

“We believe that nanoparticles embedded in tumours can absorb X-rays efficiently at particular frequencies, resulting in electron ejections that can kill malignant cells,” she continued. “From X-ray spectroscopy, we can predict those energies and which atoms or molecules are likely to be most effective.”

CT scanner

The space spin-off will hopefully lead to better, life-saving scans.

Reducing patient’s radiation exposure

“From a basic physics point of view, the use of radiation in medicine is highly indiscriminate,” Pradhan added. “Really, there has been no fundamental advance in X-ray production since the 1890s, when Roentgen invented the X-ray tube, which produces X-rays over a very wide range.”

No fundamental advance, that is, until now.

Nahar and Anil Pradhan, professor of astronomy at Ohio State, discovered that particular frequencies of X-rays cause the electrons in heavy metal atoms to vibrate and break free from their orbits around the nucleus, creating what amounts to an electrically charged gas, or plasma, around the atoms at the nanometer scale.

“Together with long-time collaborator and medical physicist Yan Yu from Thomas Jefferson University Medical College, we’ve developed the … methodology, which we hope will have far-reaching consequences for X-ray imaging and radiation therapy,” Pradhan said.

While typical therapeutic X-ray machines such as CT scanners generate full-spectrum X-rays, hospitals could employ the new technique to greatly reduce a patient’s radiation exposure.

That’s the function of the proof-of-principle device that the team has constructed. Though the working tabletop prototype needs to be further developed, these first experiments show that the effect can be used to deliver specific frequencies of X-ray radiation to heavy metal nanoparticles embedded in diseased tissue for imaging or therapy.

“This work could eventually lead to a combination of radiation therapy with chemotherapy using platinum as the active agent,” Pradhan said.

Adapted from information issued by Ohio State University.

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Neutron star bites off more than it can chew

Artist's impression of a neutron star partially devouring a massive clump of matter.

Artist's impression of a neutron star partially devouring a massive clump of matter spat out by its companion star.

ASTRONOMERS HAVE SEEN a faint star flare up at X-ray wavelengths to almost 10,000 times its normal brightness…caused, they think, by the star trying to eat a giant clump of matter.

The flare took place on a neutron star, the collapsed heart of a once much larger star, and part of a binary star system. Only 10 kilometres in diameter, the neutron star is so dense that it generates a strong gravitational field.

The clump of matter was much larger than the neutron star and came from its enormous, blue supergiant companion star.

“This was a huge bullet of gas that the star shot out, and it hit the neutron star…,” says Enrico Bozzo, ISDC Data Centre for Astrophysics, University of Geneva, Switzerland, and team leader of the research.

The flare lasted four hours. The X-rays came from the gas in the clump as it was heated to millions of degrees while being pulled into the neutron star’s intense gravity field.

Because the clump was much bigger than the neutron star, only some of it was swallowed.

An artist's impression of XMM-Newton.

An artist's impression of XMM-Newton.

A lucky observation

The European Space Agency’s XMM-Newton space observatory caught the flare during a scheduled 12.5-hour observation of the system, which is known only by its catalogue number IGR J18410-0535.

But the astronomers were not immediately aware of their catch.

The telescope works through a sequence of observations carefully planned to make the best use of its time, then sends the data to Earth.

It was about 10 days after the observation that Dr Bozzo and his colleagues received the data and quickly realised they had something special. Not only was the telescope pointing in the right direction to see the flare, but the observation had lasted long enough for them to see it from beginning to end.

“I don’t know if there is any way to measure luck, but we were extremely lucky,” says Dr Bozzo. He estimates that an X-ray flare of this magnitude can be expected a few times a year at the most for this particular star system.

The duration of the flare allowed them to estimate the size of the gas clump. It was much larger than the star, probably 16 million kilometres across—that’s about 100 billion times the volume of the Moon, yet it had probably only 1/1,000th of the Moon’s mass.

Adapted from information issued by ESA / AOES Medialab / C. Carreau.

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Aussie astronomers find stellar heavyweights

  • Many huge stars in the Milky Way cannot be seen because of intervening dust
  • University of Sydney team develops method to spot them using X-ray data
  • These giant stars live fast and die young, often in violent explosions

AN ASTRONOMY TEAM at the University of Sydney has used the bright X-ray glow from our galaxy’s most massive stars to find where they are hiding.

There are over 400 million stars in the Milky Way but only a few are truly massive. These stars emits ‘winds’ that flash outwards at over 1,000 kilometres per second and at temperatures of up to 100 million degrees.

The search project—known as “ChIcAGO” (Chasing the Identification of ASCA Galactic Objects)—is lead by Gemma Anderson from the School of Physics.

“ChIcAGO was designed to explore the unidentified X-ray sources detected with the Advanced Satellite for Cosmology and Astrophysics (ASCA), an older generation orbital X-ray telescope,” says Anderson.

Ms Anderson says the massive stars they found can be 50 times heavier than our Sun. But they have very short life spans, and may end in a supernova explosion that produces enough light to outshine the entire galaxy.

“We asked how do we find these rare and distant supernova progenitors, hidden deep in the Milky Way?

“These stars are nearly invisible to traditional optical telescopes, because the dust in … our galaxy absorbs their light,” Anderson explains.

Recent observations with NASA’s Chandra X-ray Observatory have discovered that these massive stars can be some of the brightest sources of X-ray radiation, easily shining through the galactic dust.

The ASCA satellite

The team used data from the ASCA satellite observatory.

Shocking discovery

Taking it a step further, the ChIcAGO project asked what possible process could cause a star to produce such high-energy radiation?

Anderson explains: “When X-ray radiation is detected from an astronomical object it means that [the object is] extremely hot and that particles are being accelerated to speeds near the speed of light.”

In this case the massive stars have winds that blow over 1,000 kilometres per second and are often found in binary star pairs.

“Such systems are known as colliding-wind binaries as the strong winds from these stars collide, creating extremely strong shocks that heat the stellar material to temperatures up to 100 million degrees, resulting it the production of bright and powerful X-rays,” added Anderson.

“The collisions in colliding-wind binaries are some of the most violent in our universe, only surpassed by extreme events like the death of one of these massive stars in a supernova.”

The detection of their X-ray emission is a new way of discovering massive stars that previously eluded discovery in extensive infrared and optical surveys of our galaxy.

“By searching for such high energy X-rays with Chandra we have devised an efficient way of finding the most massive stars in our galaxy,” Anderson says.

In the future, the ChIcAGO project is aiming to discover the identity of other massive stars in colliding-wind binaries, as well as their supernova remnants, allowing us the explore the life, death and evolution of these stellar giants in the Milky Way.

Other involved in the work include Bryan Gaensler (University of Sydney), David Kaplan (University of Wisconsin, Milwaukee), Bettina Posselt, Patrick Slane and Stephen Murray (Harvard-Smithsonian Center for Astrophysics, or CfA), Jon Mauerhan (California Institute of Technology), Robert Benjamin (University of Wisconsin, Whitewater), Crystal Brogan (National Radio Astronomy Observatory), Deepto Chakrabarty (Massachusetts Institute of Technology), Jeremy Drake (CfA), Janet Drew (University of Hertfordshire), Jonathan Grindlay and Jaesub Hong (CfA), Joseph Lazio (Naval Research Laboratory), Julia Lee (CfA), Danny Steeghs (University of Warwick), and Marten van Kerkwijk (University of Toronto).

The results have been published in The Astrophysical Journal.

Adapted from information issued by the University of Sydney. Images courtesy NASA / ESA.

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Giant ring of black holes

Composite image of Arp 147

This image of galaxy pair Arp 147 combines X-ray and visible light data to reveal the presence of black holes. Gas being sucked into the black holes emits X-rays (shown as pink).

  • Arp 147 is a pair of galaxies that collided, triggering a wave of star formation
  • Many of the new stars exploded as supernovae, some forming black holes.
  • Ring of these black holes can be seen in Chandra X-ray Observatory images

JUST IN TIME FOR VALENTINE’S DAY comes a new image of a ring — not of jewels, but of black holes.

The image above shows Arp 147, a pair of interacting galaxies located about 430 million light-years from Earth. The image is a combination of X-rays from the NASA’s Chandra X-ray Observatory (pink) and optical data from the Hubble Space Telescope (red, green, blue).

Arp 147 contains the remnant of a spiral galaxy (right) that collided with the elliptical galaxy on the left. This collision produced an expanding wave of star formation that shows up as a blue ring containing in abundance of massive young stars. These stars race through their evolution in a few million years or less and explode as supernovae, leaving behind neutron stars and black holes.

A fraction of the neutron stars and black holes will have companion stars, and may become bright X-ray sources as they pull in gas from their companions.

The nine X-ray sources scattered around the ring in Arp 147 are so bright that they must be black holes, with masses that are likely 10 to 20 times that of the Sun.

An X-ray source is also detected in the nucleus of the red galaxy on the left and may be powered by a poorly fed supermassive black hole. This source is not obvious in the composite image but can easily be seen in the X-ray image.

Other objects unrelated to Arp 147 are also visible—a foreground star in the lower left of the image and a background quasar as the pink source above and to the left of the red galaxy.

Infrared observations with NASA’s Spitzer Space Telescope and ultraviolet observations with NASA’s Galaxy Evolution Explorer (GALEX) have enabled estimates to be made of the rate of star formation in the ring.

These estimates, combined with the use of models for the evolution of binary stars have enabled scientists to conclude that the most intense star formation may have ended some 15 million years ago, in Earth’s time frame.

The results were published in the October 1, 2010, issue of The Astrophysical Journal. The scientists involved were Saul Rappaport and Alan Levine from the Massachusetts Institute of Technology, David Pooley from Eureka Scientific, and Benjamin Steinhorn, also from MIT.

Adapted from information issued by the Chandra X-ray Centre. Image credits: X-ray, NASA / CXC / MIT / S. Rappaport et al; optical, NASA / STScI.

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Birth and death in Andromeda

M31 Andromeda galaxy

The Andromeda Galaxy, seen at several wavelengths to reveal different stages of the stellar life cycle. Infrared shows reservoirs of gas in which stars are forming. Optical shows adult stars. X-rays show the violent endpoints of stellar evolution, in which individual stars explode or pairs of stars pull each other to pieces.

  • Andromeda Galaxy is the nearest large spiral galaxy
  • Contains a strange dust ring 75,000 light-years wide
  • Infrared and X-ray views show stars forming and dying

TWO SPACE TELESCOPES have combined forces to show the Andromeda Galaxy in a new light.

Using data from the European Space Agency’s (ESA) Herschel and XMM-Newton telescopes, the image shows the light of newborn stars and X-ray emission from dying stars.

Andromeda, also known as M31, is the nearest large spiral galaxy and is similar to our own Milky Way. Both contain several hundred billion stars.

Herschel was used to produce the most detailed far-infrared image of Andromeda ever taken, showing clearly that more stars are being added to the galaxy.

Sensitive to far-infrared light, Herschel sees the clouds of cool dust and gas where stars can form. Inside these clouds are many dusty cocoons containing still-forming stars, each one pulling itself together in a slow gravitational process that can last for hundreds of millions of years.

Once a star reaches a high enough density, it will begin to shine at optical wavelengths, whereupon it will become visible to normal telescopes.

Andromeda is interesting because it shows a large ring of dust about 75,000 light-years wide encircling the centre of the galaxy. Some astronomers speculate that this ring might be a “scar” that formed after a recent collision with another galaxy.

Herschel space telescope

Artist's impression of the Herschel space telescope

The new Herschel image reveals yet more intricate details, with at least five concentric rings of star-forming dust apparent.

X-rays of stellar corpses

Superimposed on the infrared image is an X-ray view taken almost simultaneously by XMM-Newton. Whereas infrared shows the beginnings of star formation, X-rays usually show the endpoints of stellar evolution.

XMM-Newton highlights hundreds of X-ray sources within Andromeda, many of them clustered around the centre, where stars are more crowded together.

Some of the X-ray sources reveal shockwaves rolling through space from exploded stars. Others indicate pairs of stars locked in a gravitational fight to the death.

In the latter case, one star has already died and is pulling gas from its still-living companion. As the gas falls through space, it heats up and gives off X-rays.

The living star will eventually be greatly depleted, having had much of its mass torn from it by the stronger gravity of its denser partner. As the stellar corpse wraps itself in this stolen gas, it could explode.

Both the infrared and X-ray images show information that is impossible to collect from the ground because these wavelengths are absorbed by Earth’s atmosphere.

Adapted from information issued by ESA. Image credits: Infrared, ESA / Herschel / PACS / SPIRE /J. Fritz, U. Gent; X-rays, ESA / XMM-Newton / EPIC / W. Pietsch, MPE; optical, R. Gendler.

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Crab’s candle starts to flicker

  • Crab Nebula is 6,500 light-years from Earth
  • It is the remains of an exploded star (a supernova)
  • Now shown to unexpectedly vary its energy output

DATA FROM SEVERAL NASA satellites has astonished astronomers by revealing unexpected changes in X-ray emission from the Crab Nebula, once thought to be the steadiest high-energy source in the sky.

“For 40 years, most astronomers regarded the Crab as a standard candle,” said Colleen Wilson-Hodge, an astrophysicist at NASA’s Marshall Space Flight Centre, who presented the findings recently at the American Astronomical Society meeting in Seattle.

“Now, for the first time, we’re clearly seeing how much our candle flickers.”

The Crab Nebula is the wreckage of an exploded star whose light reached Earth in 1054. Located 6,500 light-years away, it is one of the most studied objects in the sky.

At the heart of the expanding gas cloud lies what’s left of the original star’s core, a superdense neutron star that spins 30 times a second. All of the Crab’s high-energy emissions are thought to be the result of physical processes that tap into this rapid spin.

For decades, astronomers have regarded the Crab’s X-ray emissions as so stable that they’ve used it to calibrate space-borne instruments. They also customarily describe the emissions of other high-energy sources in “millicrabs,” a unit derived from the nebula’s output.

Crab Nebula

This view of the Crab Nebula comes from the Hubble Space Telescope and spans 12 light-years. The supernova remnant, located 6,500 light-years away, is among the best-studied objects in the sky. Image courtesy NASA / ESA / ASU / J. Hester.

“The Crab Nebula is a cornerstone of high-energy astrophysics,” said team member Mike Cherry at Louisiana State University (LSU), “and this study shows us that our foundation is slightly askew.”

Satellite tag teams

The story unfolded when Cherry and Gary Case, also at LSU, first noticed the Crab’s dimming in observations by the Gamma-ray Burst Monitor (GBM) aboard NASA’s Fermi Gamma-ray Space Telescope.

The team then analysed GBM observations of the object from August 2008 to July 2010 and found an unexpected but steady decline of several percent at four different “hard” X-ray energies.

With the Crab’s apparent constancy well established, the scientists needed to prove that the fadeout was real and was not an instrumental problem associated with the GBM.

“If only one satellite instrument had reported this, no one would have believed it,” Wilson-Hodge said.

Graph showing multi-wavelength observations of the Crab Nebula

Data from four satellites show that the Crab Nebula's energy output has varied. Powerful gamma-ray flares (pink vertical lines) have been detected as well. Graph courtesy NASA Goddard Space Flight Centre.

So the team amassed data from the fleet of sensitive X-ray observatories now in orbit—NASA’s Rossi X-Ray Timing Explorer (RXTE) and Swift satellites and the European Space Agency’s International Gamma-Ray Astrophysics Laboratory (INTEGRAL).

The results confirm a real intensity decline of about 7 percent at certain energy ranges. They also show that the Crab has brightened and faded by as much as 3.5 percent a year since 1999.

The scientists say that astronomers will need to find new ways to calibrate instruments in flight and to explore the possible effects of the inconstant Crab on past findings.

Showing some flare

Fermi’s other instrument, the Large Area Telescope, has detected unprecedented gamma-ray flares from the Crab, showing that it is also surprisingly variable at much higher energies.

The nebula’s power comes from the central neutron star, which is also a pulsar that emits fast, regular radio and X-ray pulses. This pulsed emission exhibits no changes associated with the decline, so it cannot be the source.

Instead, researchers suspect that the long-term changes probably occur in the nebula’s central light-year, but observations with future telescopes will be needed to know for sure.

Adapted from information issued by NASA MSFC.

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Blast blinds telescope

Gamma-ray burst GRB100621A

The brightest gamma-ray burst ever seen in X-rays temporarily blinded Swift's X-ray Telescope on 21 June 2010. This image merges the X-rays (red to yellow) with the same view from Swift's Ultraviolet/Optical Telescope, which showed nothing extraordinary.

  • Blast of X-rays from stellar explosion
  • Temporarily overwhelmed NASA’s Swift space observatory
  • Largest X-ray blast ever seen by Swift

A blast of the brightest X-rays ever detected from beyond our Milky Way galaxy’s neighbourhood temporarily blinded the X-ray eye on NASA’s Swift space observatory last month.

The X-rays had travelled through space for 5 billion years before slamming into and overwhelming Swift’s X-ray Telescope on 21 June.

The blindingly bright blast came from a gamma-ray burst (GRB), a violent eruption of energy from the explosion of a massive star morphing into a new black hole.

“This gamma-ray burst is by far the brightest light source ever seen in X-ray wavelengths at cosmological distances,” said David Burrows, senior scientist and professor of astronomy and astrophysics at Penn State University and the lead scientist for Swift’s X-ray Telescope.

Although the Swift satellite was designed specifically to study GRBs, the instrument was not designed to handle an X-ray blast this bright.

“The intensity of these X-rays was unexpected and unprecedented,” said Neil Gehrels, Swift’s principal investigator at NASA’s Goddard Space Flight Centre. He said the burst, named GRB 100621A, is the brightest X-ray source that Swift has detected since the observatory began work in early 2005.

Artist's impression of the Swift space observatory

The Swift space observatory (artist's impression) can swivel quickly in space to catch the fast flashes of energy from gamma-ray bursts.

“Just when we were beginning to think that we had seen everything that gamma-ray bursts could throw at us, this burst came along to challenge our assumptions about how powerful their X-ray emissions can be,” Gehrels said.

Blast so strong, Swift’s software shut down

“The burst was so bright when it first erupted that our data-analysis software shut down,” said Phil Evans, a postdoctoral research assistant at the University of Leicester in the United Kingdom who wrote parts of Swift’s X-ray-analysis software.

“So many photons were bombarding the detector each second that it just couldn’t count them quickly enough. It was like trying to use a rain gauge and a bucket to measure the flow rate of a tsunami.”

The software soon resumed capturing the evolution of the burst over time, and Evans recovered the data that Swift had detected during the software’s brief shutdown. The scientists then were able to measure the blast’s X-ray brightness at 143,000 X-ray photons per second during its fleeting period of greatest brightness.

That’s more than 140 times brighter than the brightest continuous X-ray source in the sky—a neutron star that is more than 500,000 times closer to Earth than the gamma-ray burst, and that sends a ‘mere’ 10,000 photons per second streaming toward Swift’s telescopes.

Artist's impression of a gamma-ray burst

Artist's impression of a gamma-ray burst, thought to occur when a large star explodes and implodes to become a black hole.

Rapid response to energy bursts

Gamma-ray bursts typically begin with a bright flash of high-energy gamma-rays and X-rays, then fade away like a fireworks display, sometimes leaving behind a disappearing afterglow in less-energetic wavelengths, including optical and ultraviolet.

Surprisingly, although the energy from this burst was the brightest ever in X-rays, it was merely ordinary in optical and ultraviolet wavelengths.

“We never thought we’d see anything this bright,” Burrows said.

The Swift observatory was launched in November 2004 and was fully operational by January 2005. Swift carries three main instruments—the Burst Alert Telescope, the X-ray Telescope, and the Ultraviolet/Optical Telescope. The Burst Alert Telescope provides rapid initial location data.

The three telescopes give Swift the ability to do almost immediate follow-up observations of most gamma-ray bursts because Swift can rotate so quickly to point toward the source of the gamma-ray signal.

Adapted from information issued by Penn State / Barbara K. Kennedy / NASA / Swift / Stefan Immler.

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