Atacama Array (ALMA) detects star forming molecular gas

An artist’s conception of the environment around GRB 020819B based on ALMA observations. 

Image Credit: NAOJ

Using the Atacama Large Millimeter/submillimeter Array (ALMA), a team of researchers reports the first-ever detection of molecular gas, the fuel for star formation, in two galaxies that were previously rocked by gamma ray bursts (GRBs), the brightest explosions in the Universe.

These new observations revealed that the molecular gas was concentrated toward the centers of the galaxies, while the GRBs occurred in unusual environments that were surprisingly bereft of gas yet rich in dust.

The researchers speculate that the dearth of molecular gas around the GRBs was due to strong ultraviolet (UV) radiation from young, massive stars, which can break apart the molecules of gas while leaving the dust relatively undisturbed.

The GRBs, dubbed GRB 020819B and GRB 051022, are located approximately 4.3 billion and 6.9 billion light-years away from Earth, respectively.

Astronomer Bunyo Hatsukade, assistant professor at the Chile Observatory of the National Astronomical Observatory of Japan (NAOJ), led the research group that studied the GRB host galaxies. The results are published in the journal Nature.

ALMA's unprecedented sensitivity made it possible to make the first detection ever of carbon monoxide (CO) gas in a GRB host galaxy.

ALMA's unparalleled high resolution also revealed GRB 020819B occurred in a galaxy where the molecular gas was concentrated at the nuclear region while dust was concentrated at the site of the GRB.

The ratio of dust to molecular gas at the GRB site is ten or more times higher than in normal environments. It is the first time that the spatial distribution of molecular gas and dust in the GRB host galaxies is revealed.

Currently, GRBs are classified as either long- or short-duration.

• A long-duration GRB, which lasts two seconds or longer, is believed to be generated by the supernova explosion of a star 40 or more times the mass of our Sun. 
• Short GRBs last less than two seconds and are associated with the collision and merger of neutron stars.

Stellar explosion on outer reaches of Universe provides clues about black hole formation

Top left box (a): Image of the field of the GRB121024A captured by the Very Large Telescope (VLT), Chile. 

The GRB121024A is the point marked by the dotted lines.

The glow of the GRB121024A in the image does not correspond to its distance from the Earth. 

In fact, as can be seen, the GRB121024A is one of the brightest objects in the field, despite being one of the most distant, if not the most distant one, in the image.

So the point marked corresponds to the explosion of a star about ~11,000 million years ago when the age of the Universe was only one third of what it is now. 

General box (b): Artist's impression of the GRB121024A.

It is possible to see the jets emerging from the dying star in the center of which a black hole would form. The blue wave spread by the jet represents the circular polarization detected.

Acknowledgements: NASA, Goddard Space Flight Center/S. Wiessinger. Credit: UPV/EHU

On 24 October 2012 observatories across the world were alerted about a huge stellar explosion, the GRB121024A.

However, only the European Southern Observatory using its Very Large Telescope located in Chile managed to take accurate polarimetric measurements of the phenomenon.

The data obtained on that explosion, which took place about 11,000 million years ago, have made it possible to reconstruct how a black hole is formed.

The work, which has had the participation of the Ikerbasque researcher Javier Gorosabal, co-director of the Associated Unit with the Institute of Astrophysics of Andalusia /CSIC-UPV /EHU, has been published in the prestigious journal Nature.

There is no other event in the cosmos that can compete in terms of energy and intensity with stellar explosions on the outer reaches of the universe and which are known as LGRBs (Long Gamma-Ray Bursts): in just one second a single GRB can emit as many as hundreds of stars like the Sun during its 10,000-million-year-lifetime.

For the last decade astrophysicists have been in possession of strong evidence that LGRBs occur when the so-called massive stars burst; these are huge stars with masses of up to hundreds of times bigger than that of the Sun and which, moreover, spin rapidly on a rotation axis.

As these stars are massive and spin, they do not explode like a normal star, which does so radially, as a ball does when it deflates, for example.

The implosion of these huge stars would produce, according to theoretical models, a huge spinning top, which would turn in the way that water rotates down the plughole of a basin, until a black hole is finally formed.

The energy given off by this gigantic explosion would be emitted in two jets displaying a high level of energy and which would be aligned with the rotation axis of the dying star.

What is more, all these stars have magnetic fields. And these are intensified further if they rotate rapidly, as in the case of the LGRBs.

So during the internal collapse of the star towards the central black hole, the magnetic fields of the star would also swirl around the star's rotation axis, and during the collapse of the star, a powerful "magnetic geyser" would be produced and be ejected from the environment of the black hole that is being formed; the effects of this can be felt at distances of billions of kilometres.

Image of the GRB121024A captured by means of the polarimeter fitted onto the FORS2 instrument of the VLT. 

The polarimeter provides two images for each object in the field of vision.

The polarized objects appear considerably brighter in one band than in the other. The non-polarized objects, the vast majority, display the same intensity in the upper and lower band.

The object indicted by the arrow is the GRB121024A which displayed a circular polarization of 0.6%. 

Credit: Wiersema et al. 2014, Nature, DOI 10.1038/nature13237.

This complex scenario led one to predict that the light emitted during the explosion of the star must have been circularly polarized as if it were a screw, and that is what, for the first time, the authors have detected in Chile: a circularly polarized light that is the direct consequence of a black hole "recently" created on the outer reaches of the Universe and which has been confirmed by the theoretical model.

What is more, an optical circular polarization to such a high degree had never been detected, and nor had one been detected in such a distant source. All this indicates that the GRB121024A is an extraordinary event.

The VLT is one of the largest and best equipped telescopes in the world; it makes use of the exceptional astronomical observation conditions of the Atacama desert.

That is why the use of the VLT is very limited and is regulated by a highly competitive process in which every six months an international committee selects the best proposals for observation submitted.

So the only way to access these technologically state-of-the-art facilities is by means of powerful international consortia. 27 institutions belonging to 13 countries have participated in the study published by the prestigious journal Nature.

More information: K. Wiersema, S. Covino, K. Toma, A.J. van der Horst, K. Varela, M. Min, J. Greiner, R.L.C. Starling, N.R. Tanvir, R.A.M.J. Wijers, S. Campana, P.A. Curra, Y. Fan, J.P.U. Fynbo, J. Gorosabel, A. Gomboc, D. Götz, J. Hjorth, Z.P. Jin, S. Kobayashi, C. Kouveliotou, C. Mundell, P.T.O'Brien, E. Pian, A. Rowlinson, D.M. Russell, R. Salvaterra, S. Di Serego Alighieri, G. Tagliafferri, S.D. Vergani, J. Eliott, C. Fariña, O.E. Hartoog, R. Karjalainen, S. Klose, F. Knust, A.J. Levan, P. Schady, V. Sudilovsky, & R. Willingale. "Circular Polarization in the optical afterglow of GRB121024A". Nature, 2014, DOI: 10.1038/nature13237

Cosmic Flash may reveal Birth of a Black Hole

A computer-generated image of the light distortions created by a black hole. Credit: Alain Riazuelo, IAP/UPMC/CNRS

When a massive star exhausts its fuel, it collapses under its own gravity and produces a black hole, an object so dense that not even light can escape its gravitational grip.

According to a new analysis by an astrophysicist at the California Institute of Technology (Caltech), just before the black hole forms, the dying star may generate a distinct burst of light that will allow astronomers to witness the birth of a new black hole for the first time.

Tony Piro

Tony Piro, a postdoctoral scholar at Caltech, describes this signature light burst in a paper published in the May 1 issue of the Astrophysical Journal Letters.

While some dying stars that result in black holes explode as gamma-ray bursts, which are among the most energetic phenomena in the universe, those cases are rare, requiring exotic circumstances, Piro explains.

"We don't think most run-of-the-mill black holes are created that way." In most cases, according to one hypothesis, a dying star produces a black hole without a bang or a flash: the star would seemingly vanish from the sky—an event dubbed an unnova. "You don't see a burst," he says. "You see a disappearance."

But, Piro hypothesizes, that may not be the case. "Maybe they're not as boring as we thought," he says.

According to well-established theory, when a massive star dies, its core collapses under its own weight. As it collapses, the protons and electrons that make up the core merge and produce neutrons.

For a few seconds—before it ultimately collapses into a black hole—the core becomes an extremely dense object called a neutron star, which is as dense as the sun would be if squeezed into a sphere with a radius of about 10 kilometers (roughly 6 miles).

This collapsing process also creates neutrinos, which are particles that zip through almost all matter at nearly the speed of light.

As the neutrinos stream out from the core, they carry away a lot of energy—representing about a tenth of the sun's mass (since energy and mass are equivalent, per E = mc2).

According to a little-known paper written in 1980 by Dmitry Nadezhin of the Alikhanov Institute for Theoretical and Experimental Physics in Russia, this rapid loss of mass means that the gravitational strength of the dying star's core would abruptly drop.

When that happens, the outer gaseous layers—mainly hydrogen—still surrounding the core would rush outward, generating a shock wave that would hurtle through the outer layers at about 1,000 kilometers per second (more than 2 million miles per hour).

Stan Woosley

Using computer simulations, two astronomers at UC Santa Cruz, Elizabeth Lovegrove and Stan Woosley, recently found that when the shock wave strikes the outer surface of the gaseous layers, it would heat the gas at the surface, producing a glow that would shine for about a year—a potentially promising signal of a black-hole birth.

Although about a million times brighter than the sun, this glow would be relatively dim compared to other stars.

"It would be hard to see, even in galaxies that are relatively close to us," says Piro.

But now Piro says he has found a more promising signal. In his new study, he examines in more detail what might happen at the moment when the shock wave hits the star's surface, and he calculates that the impact itself would make a flash 10 to 100 times brighter than the glow predicted by Lovegrove and Woosley.

"That flash is going to be very bright, and it gives us the best chance for actually observing that this event occurred," Piro explains. "This is what you really want to look for."

Such a flash would be dim compared to exploding stars called supernovae, for example, but it would be luminous enough to be detectable in nearby galaxies, he says.

The flash, which would shine for 3 to 10 days before fading, would be very bright in optical wavelengths—and at its very brightest in ultraviolet wavelengths.

Piro estimates that astronomers should be able to see one of these events per year on average. Surveys that watch the skies for flashes of light like supernovae—surveys such as the Palomar Transient Factory (PTF), led by Caltech—are well suited to discover these unique events, he says.

The intermediate Palomar Transient Factory (iPTF), which improves on the PTF and just began surveying in February, may be able to find a couple of these events per year.

Neither survey has observed any black-hole flashes as of yet, says Piro, but that does not rule out their existence. "Eventually we're going to start getting worried if we don't find these things." But for now, he says, his expectations are perfectly sound.

NASA Image: Neutron Star Collision

Nasa have released an artist's impression of two neutron stars colliding to produce a gamma ray burst. 

Earth was blasted by a high-energy burst of radiation from space in the 8th century, scientists believe. 

Gamma ray bursts are the most powerful explosions known in the universe. 

Each one corresponds to around a thousand Earths being vapourised into pure energy in seconds. 

Picture: Nasa

The MAGIC Cherenkov Telescope Array

The MAGIC Collaboration has built in 2001–2003 a first large atmospheric imaging Cherenkov telescope, MAGIC-I, with a mirror surface of 236 sq.m. and equipped with photo-multiplier tubes of optimal efficiency.

In 2009, a second telescope of essentially the same characteristics was added; MAGIC-II was installed at a distance of 85m from MAGIC-I.

With the accent of these instruments on large mirror surface and best light collection, cosmic gamma-rays at an energy threshold lower than any existing or planned terrestrial gamma-ray telescope have become accessible. So far achieved has been a threshold of 25 GeV.

Mysterious Gamma-ray beams blast from Milky Way's centre

This artist's conception shows an edge-on view of the Milky Way galaxy. 

Newly discovered gamma-ray jets (pink) extend for 27,000 light-years above and below the galactic plane, and are tilted at an angle of 15 degrees. 

Previously known gamma-ray bubbles are shown in purple. The bubbles and jets suggest that our galactic center was much more active in the past than it is today. Credit: David A. Aguilar (CfA)

 As galaxies go, our Milky Way is pretty quiet. Active galaxies have cores that glow brightly, powered by supermassive black holes swallowing material, and often spit twin jets in opposite directions. 

In contrast, the Milky Way's center shows little activity. But it wasn't always so peaceful. New evidence of ghostly gamma-ray beams suggests that the Milky Way's central black hole was much more active in the past.

"These faint jets are a ghost or after-image of what existed a million years ago," said Meng Su, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and lead author of a new paper in the Astrophysical Journal.

"They strengthen the case for an active galactic nucleus in the Milky Way's relatively recent past," he added.

The two beams, or jets, were revealed by NASA's Fermi space telescope. They extend from the galactic center to a distance of 27,000 light-years above and below the galactic plane. They are the first such gamma-ray jets ever found, and the only ones close enough to resolve with Fermi.

The newfound jets may be related to mysterious gamma-ray bubbles that Fermi detected in 2010. Those bubbles also stretch 27,000 light-years from the center of the Milky Way. However, where the bubbles are perpendicular to the galactic plane, the gamma-ray jets are tilted at an angle of 15 degrees. This may reflect a tilt of the accretion disk surrounding the supermassive black hole.

"The central accretion disk can warp as it spirals in toward the black hole, under the influence of the black hole's spin," explained co-author Douglas Finkbeiner of the CfA. "The magnetic field embedded in the disk therefore accelerates the jet material along the spin axis of the black hole, which may not be aligned with the Milky Way."

The two structures also formed differently. The jets were produced when plasma squirted out from the galactic center, following a corkscrew-like magnetic field that kept it tightly focused. The gamma-ray bubbles likely were created by a "wind" of hot matter blowing outward from the black hole's accretion disk. As a result, they are much broader than the narrow jets.

Both the jets and bubbles are powered by inverse Compton scattering. In that process, electrons moving near the speed of light collide with low-energy light, such as radio or infrared photons. The collision increases the energy of the photons into the gamma-ray part of the electromagnetic spectrum.

The discovery leaves open the question of when the Milky Way was last active. A minimum age can be calculated by dividing the jet's 27,000-light-year length by its approximate speed. However, it may have persisted for much longer.

"These jets probably flickered on and off as the supermassive black hole alternately gulped and sipped material," said Finkbeiner.

It would take a tremendous influx of matter for the galactic core to fire up again. Finkbeiner estimates that a molecular cloud weighing about 10,000 times as much as the Sun would be required.

"Shoving 10,000 suns into the black hole at once would do the trick. Black holes are messy eaters, so some of that material would spew out and power the jets," he said.

Journal reference: Astrophysical Journal

Provided by Harvard-Smithsonian Center for Astrophysics

NASA Camilla: One small step for a rubber chicken - video

Last month, when the sun unleashed the most intense radiation storm since 2003, peppering satellites with charged particles and igniting strong auroras around both poles, a group of high school students in Bishop, California, knew just what to do.

They launched a rubber chicken.

The students inflated a helium balloon and used it to send the fowl, named "Camilla," to an altitude of 120,000 ft where she was exposed to high-energy solar protons at point blank range.

"We equipped Camilla with sensors to measure the radiation," says Sam Johnson (age 16) of Bishop Union High School's Earth to Sky student group. "At the apex of our flight, the payload was above 99% of Earth's atmosphere."

Launching a rubber chicken into a solar storm might sound strange, but the students had good reason: They're doing an astrobiology project.

"Later this year, we plan to launch a species of microbes to find out if they can live at the edge of space," explains team member Rachel Molina (age 17). "This was a reconnaissance flight."

Many space enthusiasts are already familiar with Camilla. She's the mascot of NASA's Solar Dynamics Observatory. With help from her keeper, Romeo Durscher of Stanford University, Camilla corresponds with more than 20,000 followers on Twitter, Facebook, and Google+, filling them in on the latest results from NASA's heliophysics missions.

"Camilla's trip to the stratosphere gave us a chance to talk to thousands of people about the radiation storm," says Durscher.

On the outside of her space suit (knitted by Cynthia Coer Butcher from Blue Springs, Missouri), Camilla wore a pair of radiation badges, the same kind medical technicians and nuclear workers wear to assess their dosages.

Read more at NASA

NASA Fermi: Mysterious Objects at the Edge of the Electromagnetic Spectrum

From end to end, the newly discovered gamma-ray bubbles extend 50,000 light-years, or roughly half of the Milky Way's diameter, as shown in this illustration. 

Hints of the bubbles' edges were first observed in X-rays (blue) by ESA's ROSAT, a Germany-led mission operating in the 1990s. 

The gamma rays mapped by Fermi (magenta) extend much farther from the galaxy's plane. 

Credit: NASA's Goddard Space Flight Center.

The human eye is crucial to astronomy. Without the ability to see, the luminous universe of stars, planets and galaxies would be closed to us, unknown forever. Nevertheless, astronomers cannot shake their fascination with the invisible.

Outside the realm of human vision is an entire electromagnetic spectrum of wonders. Each type of light from radio waves to gamma-rays reveals something unique about the universe. Some wavelengths are best for studying black holes; others reveal newborn stars and planets; while others illuminate the earliest years of cosmic history.

NASA has many telescopes "working the wavelengths" up and down the electromagnetic spectrum. One of them, the Fermi Gamma-Ray Telescope orbiting Earth, has just crossed a new electromagnetic frontier.

"Fermi is picking up crazy-energetic photons," says Dave Thompson, an astrophysicist at NASA's Goddard Space Flight Center. "And it's detecting so many of them we've been able to produce the first all-sky map of the very high energy universe."

"This is what the sky looks like near the very edge of the electromagnetic spectrum, between 10 billion and 100 billion electron volts."

The light we see with human eyes consists of photons with energies in the range 2 to 3 electron volts. The gamma-rays Fermi detects are billions of times more energetic, from 20 million to more than 300 billion electron volts.

These gamma-ray photons are so energetic, they cannot be guided by the mirrors and lenses found in ordinary telescopes. Instead Fermi uses a sensor that is more like a Geiger counter than a telescope.

If we could wear Fermi's gamma ray "glasses," we'd witness powerful bullets of energy - individual gamma rays - from cosmic phenomena such as supermassive black holes and hypernova explosions. The sky would be a frenzy of activity.

Fermi telescope: Gamma-ray bursts' highest power side unveiled

Detectable for only a few seconds but possessing enormous energy, gamma-ray bursts are difficult to capture because their energy does not penetrate the Earth's atmosphere.

Now, thanks to an orbiting telescope, astrophysicists are filling in the unknowns surrounding these bursts and uncovering new questions.

The Fermi Gamma-Ray Space Telescope, formerly called the Gamma-Ray Large Area Space Telescope, launched on June 11, 2008. As part of its mission, the telescope records any gamma-ray bursts within its viewing area.

"Fermi is lucky to measure the highest energy portion of the gamma-ray burst emission, which last for hundreds to thousands of seconds -- maybe 20 minutes," said Péter Mészáros, Eberly Chair Professor of Astronomy and Astrophysics and Physics, Penn State.

Most gamma-ray bursts occur when stars that are more than 25 times larger than our sun come to the end of their lives. When the internal nuclear reaction in these stars ends, the star collapses in on itself and forms a black hole. The outer envelope of the star is ejected forming a supernova.

"The black hole is rotating rapidly and as it is swallowing the matter from the star, the rotation ejects a jet of material through the supernova envelope," said Mészáros.

This jet causes the gamma-ray burst, which briefly becomes the brightest thing in the sky. However, unlike supernovas that radiate in all directions, gamma-ray bursts radiate in a very narrow area, and Fermi sees only jets ejecting in its direction.

This, however, is the direction in which they send their highest energy photons. Any gamma-ray bursts on the other side of the black hole or even off at an angle are invisible to the telescope.

"We actually miss about 500 gamma-ray bursts for every one we detect," Mészáros told attendees today at the annual meeting of the American Association for the Advancement of Science in Vancouver, British Columbia.

The gamma-ray bursts that Fermi has seen have allowed astrophysicists to clarify previous theories about gamma-ray bursts.

"We have been able to rule out the simplest version of theories which combine quantum mechanics with gravity, although others remain to be tested," said Mészáros.

Mészáros notes that Fermi and other programs like the SWIFT telescope have shown that gamma-ray bursts last longer than we thought they did and that there are long and short gamma-ray bursts.

Read more about the SWIFT Telescope discovery here

ESA Planck and Fermi: Galactic Haze

This all-sky image shows the distribution of the Galactic Haze seen by ESA's Planck mission at microwave frequencies superimposed over the high-energy sky as seen by NASA's Fermi Gamma-ray Space Telescope.

The Planck data (shown here in red and yellow) correspond to the Haze emission at frequencies of 30 and 44 GHz, extending from and around the Galactic Centre.

The Fermi data (shown here in blue) correspond to observations performed at energies between 10 and 100 GeV and reveal two bubble-shaped, gamma-ray emitting structures extending from the Galactic Centre.

The two emission regions seen by Planck and Fermi at two opposite ends of the electromagnetic spectrum correlate spatially quite well and might indeed be a manifestation of the same population of electrons via different radiation processes.

Synchrotron emission associated with the Galactic Haze seen by Planck exhibits distinctly different characteristics from the synchrotron emission seen elsewhere in the Milky Way. Diffuse synchrotron emission in the Galaxy is interpreted as radiation from highly energetic electrons that have been accelerated in shocks created by supernova explosions.

Compared to this well-studied emission, the Galactic Haze has a 'harder' spectrum, meaning that its emission does not decline as rapidly with increasing frequency.

Several explanations have been proposed for this unusual behaviour, including enhanced supernova rates, galactic winds and even annihilation of dark-matter particles. Thus far, none of them have been confirmed and the issue remains open.

The Planck image includes the mask that has been used in the analysis of the data to exclude regions with strong foreground contamination due to the Galaxy's diffuse emission. The mask also includes strong point-like sources located over the whole sky.

Credits: ESA/Planck Collaboration (microwave); NASA/DOE/Fermi LAT/D. Finkbeiner et al. (gamma rays)

RXTE Helps Pinpoint Launch of Bullets in Black Hole Jet

Radio imaging by the Very Long Baseline Array (top row), combined with simultaneous X-ray observations by NASA's RXTE (middle), captured the transient ejection of massive gas "bullets" by the black hole binary H1743-322 during its 2009 outburst.

By tracking the motion of these bullets with the VLBA, astronomers were able to link the ejection event to the disappearance of X-ray signals seen in RXTE data.

These signals, called quasi-periodic oscillations (QPOs), vanished two days earlier than the onset of the radio flare that astronomers previously had assumed signaled the ejection.

(Credit: NRAO and NASA's Goddard Space Flight Center).

NASA Fermi Tycho Supernova: Cosmic Mystery

Gamma rays detected by NASA's Fermi space telescope show that the remnant of Tycho's supernova shines in the highest-energy form of light. 

This portrait of the shattered star includes gamma rays (magenta), X-rays (yellow, green, and blue), infrared (red) and optical data.

CREDIT: Gamma ray, NASA/DOE/Fermi LAT Collaboration; X-ray, NASA/CXC/SAO; Infrared, NASA/JPL-Caltech; Optical, MPIA, Calar Alto, O. Krause et al. and DSS

A well-known exploded star that is pumping out powerful gamma rays may be the celestial smoking gun astronomers have in the search for the origins of some of the fastest-moving particles in the universe, a new study reports.

NASA's Fermi space telescope has detected gamma rays — the highest-energy form of light — emanating from the shattered husk of Tycho's supernova, a star that exploded in 1572.

The find could help astronomers pinpoint the origin of cosmic rays, super-speedy subatomic particles that crash constantly into Earth's atmosphere, researchers said.

Astronomy Image: Sculptor Group of Galaxies

NGC 253 is not only one of the brightest spiral galaxies visible, it is also one of the dustiest.

Discovered in 1783 by Caroline Herschel in the constellation of Sculptor, NGC 253 lies only about ten million light-years distant. NGC 253 is the largest member of the Sculptor Group of Galaxies, the nearest group to our own Local Group of Galaxies.

The dense dark dust accompanies a high star formation rate, giving NGC 253 the designation of starburst galaxy. Visible in the above photograph is the active central nucleus, also known to be a bright source of X-rays and gamma rays.

Gamma-rays detected by Fermi's LAT show that the remnant of Tycho's supernova shines in the highest-energy form of light. 

This portrait of the shattered star includes gamma rays (magenta), X-rays (yellow, green, and blue), infrared (red) and optical data. (Credit: Gamma ray, NASA/DOE/Fermi LAT Collaboration; X-ray, NASA/CXC/SAO; Infrared, NASA/JPL-Caltech; Optical, MPIA, Calar Alto, O. Krause et al. and DSS).

In early November 1572, observers on Earth witnessed the appearance of a "new star" in the constellation Cassiopeia, an event now recognised as the brightest naked-eye supernova in more than 400 years.

It's often called "Tycho's supernova" after the great Danish astronomer Tycho Brahe, who gained renown for his extensive study of the object.

Now, years of data collected by NASA's Fermi Gamma-Ray Space Telescope reveal that the shattered star's remains shine in high-energy gamma rays.

The detection gives astronomers another clue in understanding the origin of cosmic rays, subatomic particles - mainly protons - that move through space at nearly the speed of light.

Exactly where and how these particles attain such incredible energies has been a long-standing mystery because charged particles speeding through the galaxy are easily deflected by interstellar magnetic fields. This makes it impossible to track cosmic rays back to their sources.

"Fortunately, high-energy gamma rays are produced when cosmic rays strike interstellar gas and starlight. These gamma rays come to Fermi straight from their sources," said Francesco Giordano at the University of Bari and the National Institute of Nuclear Physics in Italy. He is the lead author of a paper describing the findings in the Dec. 7 edition of The Astrophysical Journal Letters.

Better understanding the origins of cosmic rays is one of Fermi's key goals. Its Large Area Telescope (LAT) scans the entire sky every three hours, gradually building up an ever-deeper view of the gamma-ray sky. Because gamma rays are the most energetic and penetrating form of light, they serve as signposts for the particle acceleration that gives rise to cosmic rays.

"This detection gives us another piece of evidence supporting the notion that supernova remnants can accelerate cosmic rays," said co-author Stefan Funk, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), jointly located at SLAC National Accelerator Laboratory and Stanford University, Calif.

In 1949, physicist Enrico Fermi - the satellite's namesake - suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds. In the decades that followed, astronomers showed that supernova remnants may be the galaxy's best candidate sites for this process.

NASA's Fermi Shows Highly Active Galaxies

Active galaxies called blazars make up the largest class of objects detected by Fermi's Large Area Telescope (LAT).

Massive black holes in the hearts of these galaxies fire particle jets in our direction.

Fermi team member Elizabeth Hays narrates this quick tour of blazars, which includes LAT movies showing how rapidly their emissions can change. 

Credit: NASA/Goddard Space Flight Center

NASA GRAPE: Balloon-based experiment to measure gamma rays 6,500 light years distant

Beginning Sunday, September 18, 2011 at NASA’s launch facility in Fort Sumner, New Mexico, space scientists from the University of New Hampshire will attempt to send a balloon up to 130,000 feet with a one-ton instrument payload to measure gamma rays from the Crab Pulsar, the remains of a supernova explosion that lies 6,500 light years from Earth.

The launch is highly dependent on weather and wind conditions, and the launch window closes at the end of next week.

The Gamma Ray Polarimeter Experiment (GRAPE), which was designed and built at the Space Science Center within the UNH Institute for the Study of Earth, Oceans, and Space (EOS), is an effort to apply a new type of detector technology to the study of celestial gamma rays.

Specifically, the goal of the GRAPE project is to study the polarization of gamma rays from celestial sources. “Polarized” radiation vibrates in a preferred direction, and the extent of that polarisation can provide clues to how the radiation was generated, in essence serving as a probe of the source.

Gamma rays, such as those emitted from the Crab Pulsar, are generally produced from the interactions of a highly accelerated beam of subatomic particles – massive ejections of high-energy particles that are thought to take the form of a narrow jet moving outward at nearly the speed of light.

“We think that an accelerated beam of particles is the source of the high-energy radiation from the Crab Pulsar, but the structure of that beam and the mechanism by which the radiation is generated is not entirely clear,” says mission lead scientist Mark McConnell, a professor in the SSC and chair of the UNH department of physics.

Physorg.com: Further information on NASA GRAPE and other Balloon based gamma-ray detection experiments. 

Balloon-based experiment to measure gamma rays 6,500 light years distant | ScienceBlog.com

Fermi's Latest Gamma-ray Census Highlights Cosmic Mysteries

Active galaxies called blazars constitute the single largest source class in the second Fermi LAT catalog, but nearly a third of the sources are unassociated with objects at any other wavelength. Their natures are unknown.

Credit: NASA's Goddard Space Flight Center.

Every three hours, NASA's Fermi Gamma-ray Space Telescope scans the entire sky and deepens its portrait of the high-energy universe. Every year, the satellite's scientists reanalyze all of the data it has collected, exploiting updated analysis methods to tease out new sources. These relatively steady sources are in addition to the numerous transient events Fermi detects, such as gamma-ray bursts in the distant universe and flares from the sun.

Earlier this year, the Fermi team released its second catalog of sources detected by the satellite's Large Area Telescope (LAT), producing an inventory of 1,873 objects shining with the highest-energy form of light.

"More than half of these sources are active galaxies, whose massive black holes are responsible for the gamma-ray emissions that the LAT detects," said Gino Tosti, an astrophysicist at the University of Perugia in Italy and currently a visiting scientist at SLAC National Accelerator Laboratory in Menlo Park, Calif.

One of the scientists who led the new compilation, Tosti presented a paper on the catalog at a meeting of the American Astronomical Society's High Energy Astrophysics Division in Newport, R.I.

"What is perhaps the most intriguing aspect of our new catalog is the large number of sources not associated with objects detected at any other wavelength," he noted.

Indeed, if the Fermi catalog were a recipe, the two major ingredients would be active galaxies and pure mystery. To them, add in a pinch of pulsars, a dollop of supernova remnants, and a dash of other celestial objects, such as globular star clusters and galaxies like our own Milky Way.

Astronomers delight in the possibility of finding new types of gamma-ray-emitting objects within the "unassociated sources" that constitute roughly a third of the catalog. But Fermi's LAT is revealing gamma-rays from an increasing - and sometimes, surprising - variety of astronomical objects. To highlight the range of LAT discoveries, the Fermi team created the following "top ten" list of five sources within the Milky Way and five beyond our galaxy.

NASA Swift: Gamma-Ray Bursts More Active Than Thought

From time to time, a huge explosion followed by a bright flash of light can be observed in space.

It's a colossal gamma-ray burst (GRB), emitting for a few seconds as much radiation as a million galaxies.

A new discovery made by NASA's Swift satellite showed that the extremely energetic flares that follow a gamma-ray burst (GRB) are not just space "hiccups", but in fact, they represent a continuation of the burst itself.

They are truly impressive space phenomena, as even the smallest GRB can emit the same amount of energy our Sun will emit over its expected 10 billion-year lifetime, in just one second.

The most luminous events known in the universe since the Big Bang are flashes of gamma rays, coming from seemingly random places in the sky and at random times, that last from milliseconds to many minutes and are often followed by "afterglow" emission at longer wavelengths (X-ray, UV, optical, IR and radio).

What causes such a tremendous discharge of energy? The core of a massive star collapsing to form a black hole or neutron star. The initial pulse of gamma-rays is usually followed by what was thought to be a short-lived X-ray flare.

Hans Krimm of Universities Space Research Association, Columbia, Md. and NASA's Goddard Space Flight Center in Greenbelt, Md., and eight colleagues, have been able to prove that these X-ray flares are actually a continuation of the initial pulse, which proves that the GRB central engines are active much longer than previously thought.

This was done after analyzing such an event, named GRB 060714, for its detection date of July 14, 2006 and the results showed that the prompt gamma-ray emission and the subsequent X-ray flares appear to form a continuously connected and evolving succession of events.

"This pattern points to a continuous injection of energy from the central engine, perhaps fueled by sporadic infall of material onto a black hole. 

The black hole just keeps gobbling up gas and the engine keeps spewing out energy," says Krimm.

Black Hole Devours Celestial Body

NASA's Swift satellite captured a gamma ray flash brighter than anything astronomers had previously witnessed.

The cause? Scientists believe a supermassive black hole at the center of a galaxy nearly four billion light-years distant has wrapped its gravitational tendrils around a star the size of our sun, spawning a high-energy jet of gamma radiation.

On March 28th the gamma ray burst was equivalent to the brightness of a hundred billion suns—or as the paper published today in Science describes it, "An Extremely Luminous Panchromatic Outburst from the Nucleus of a Distant Galaxy." It's believed that supermassive black holes lie at the heart of large galaxies.

"This burst produced a tremendous amount of energy over a fairly long period of time, and the event is still going on more than two and a half months later," says UC Berkeley astronomy professor and study lead Joshua Bloom.

The reason it's so bright? The energy jet is pointed directly at us. And instead of swallowing the star whole, the black hole is nibbling on it bit by bit, keeping the energy jet going.

"That's because as the black hole rips the star apart, the mass swirls around like water going down a drain, and this swirling process releases a lot of energy," explains Bloom.

Bloom surmises the black hole wasn't doing much until the star wandered by, causing a tidal disruption so violent it produced energy at never-before-seen gamma-ray levels.

Couple this with the likelihood of the jet angling in our direction, and you have a "once in 100 million years in any given galaxy” event, according to Bloom, who says he'd be surprised if another occurred "anywhere in the sky in the next decade."

NASA Chandra Observatory: Extraordinary Gamma-Ray burst

The center of this image contains an extraordinary gamma-ray burst (GRB) called GRB 110328A, observed with NASA's Chandra X-ray Observatory.

This Chandra observation confirms the association of GRB 110328A with the core of a distant galaxy and shows that it was an exceptionally long lived and luminous event compared to other GRBs.

The red cross shows the position of a faint galaxy -- located about 3.8 billion light years from Earth -- observed with NASA's Hubble Space Telescope and the Gemini-North telescope on the ground.

Allowing for experimental errors, the position of the galaxy is indistinguishable from that of the X-ray source, showing that the source is located close to the middle of the galaxy.

This is consistent with the idea, suggested by some astronomers, that a star was torn apart by a supermassive black hole at the center of the galaxy.

This idea differs from the usual interpretation for a GRB, involving the production of a jet when a black hole or neutron star forms after the collapse of a massive star or a merger between two neutron stars.

Remarkably, this "tidal disruption" event may have been caught in real time, rather than detected later from analyzing archival observations. However, this X-ray source is about a hundred times brighter than previously observed tidal disruptions.

One possible explanation for this very bright radiation is that debris from the disrupted star fell towards the black hole in a disk and the swirling, magnetized matter generated intense electromagnetic fields that created a powerful jet of particles.

If this jet is pointed toward Earth it would boost the observed brightness of the source. This scenario has already been suggested by observers to explain the bright and variable X-ray emission observed by NASA's Swift telescope.

This observation was part of a so-called target of opportunity, or TOO, led by Andrew Levan from the University of Warwick in the UK. A TOO allows the telescope to react quickly to unpredictable cosmic events, within 24 hours in some situations.

Chandra scientists and engineers can decide to alter the scheduled observations and instead point the telescope to another target if the circumstances warrant it. This process was put into place once the discovery of GRB 110328A with Swift was announced on March 28th, 2011.

The Chandra team was able to reset the telescope's schedule to observe GRB 110328A early in the morning of Monday, April 4th for a period of just over four hours.

Credits: NASA/CXC/Warwick/A.Levan et al.