Gravitational Astronomy? How Detecting Gravitational Waves Changes Everything
We’ve now had multiple detections of gravitational waves, opening up a whole new field: gravitational astronomy. We talk about the detections made so far, and how we can see the Universe in a whole new way.
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Just a couple of weeks ago, astronomers from Caltech announced their third detection of gravitational waves from the Laser Interferometer Gravitational-Wave Observatory or LIGO.
As with the previous two detections, astronomers have determined that the waves were generated when two intermediate-mass black holes slammed into each other, sending out ripples of distorted spacetime.
One black hole had 31.2 times the mass of the Sun, while the other had 19.4 solar masses. The two spiraled inward towards each other, until they merged into a single black hole with 48.7 solar masses. And if you do the math, twice the mass of the Sun was converted into gravitational waves as the black holes merged.
These gravitational waves traveled outward from the colossal collision at the speed of light, stretching and compressing spacetime like a tsunami wave crossing the ocean until they reached Earth, located about 2.9 billion light-years away.
The waves swept past each of the two LIGO facilities, located in different parts of the United States, stretching the length of carefully calibrated laser measurements. And from this, researchers were able to detect the direction, distance and strength of the original merger.
Seriously, if this isn’t one of the coolest things you’ve ever heard, I’m clearly easily impressed.
Now that the third detection has been made, I think it’s safe to say we’re entering a brand new field of gravitational astronomy. In the coming decades, astronomers will use gravitational waves to peer into regions they could never see before.
Being able to perceive gravitational waves is like getting a whole new sense. It’s like having eyes and then suddenly getting the ability to perceive sound.
This whole new science will take decades to unlock, and we’re just getting started.
As Einstein predicted, any mass moving through space generates ripples in spacetime. When you’re just walking along, you’re actually generating tiny ripples. If you can detect these ripples, you can work backwards to figure out what size of mass made the ripples, what direction it was moving, etc.
Even in places that you couldn’t see in any other way. Let me give you a couple of examples.
Black holes, obviously, are the low hanging fruit. When they’re not actively feeding, they’re completely invisible, only detectable by how they gravitational attract objects or bend light from objects passing behind them.
But seen in gravitational waves, they’re like ships moving across the ocean, leaving ripples of distorted spacetime behind them.
With our current capabilities through LIGO, astronomers can only detect the most massive objects moving at a significant portion of the speed of light. A regular black hole merger doesn’t do the trick - there’s not enough mass. Even a supermassive black hole merger isn’t detectable yet because these mergers seem to happen too slowly.
This is why all the detections so far have been intermediate-mass black holes with dozens of times the mass of our Sun. And we can only detect them at the moment that they’re merging together, when they’re generating the most intense gravitational waves.
If we can boost the sensitivity of our gravitational wave detectors, we should be able to spot mergers of less and more massive black holes.
But merging isn’t the only thing they do. Black holes are born when stars with many more times the mass of our Sun collapse in on themselves and explode as supernovae. Some stars, we’ve now learned just implode as black holes, never generating the supernovae, so this process happens entirely hidden from us.
Is there a singularity at the center of a black hole event horizon, or is there something there, some kind of object smaller than a neutron star, but bigger than an infinitely small point? As black holes merge together, we could see beyond the event horizon with gravitational waves, mapping out the invisible region within to get a sense of what’s going on down there.
We want to know about even less massive objects like neutron stars, which can also form from a supernova explosion. These neutron stars can orbit one another and merge generating some of the most powerful explosions in the Universe: gamma ray bursts. But do neutron stars have surface features? Different densities? Could we detect a wobble in the gravitational waves in the last moments before a merger?
Death From Space — Gamma-Ray Bursts Explained
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There are cosmic snipers firing at random into the unvierse. What are they and what happens if they hit us?
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Death From Space — Gamma-Ray Bursts Explained
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De-orbit of the Compton Gamma Ray Observatory
Video taken of CGRO over the Pacific Ocean during de-orbit maneuvers in June 2000. The spacecraft is seen to start tumbling as it plunges into the atmosphere.
Compton Gamma Ray Observatory - Video Learning - WizScience.com
The "Compton Gamma Ray Observatory" was a space observatory detecting light from 20 keV to 30 GeV in Earth orbit from 1991 to 2000. It featured four main telescopes in one spacecraft, covering X-rays and gamma rays, including various specialized sub-instruments and detectors. Following 14 years of effort, the observatory was launched from Space Shuttle "Atlantis" during STS-37 on April 5, 1991, and operated until its deorbit on June 4, 2000. It was deployed in low earth orbit at 450 kilometers to avoid the Van Allen radiation belt. It was the heaviest astrophysical payload ever flown at that time at 17000 kilograms.
Costing $617 million, the CGRO was part of NASA's "Great Observatories" series, along with the Hubble Space Telescope, the Chandra X-ray Observatory, and the Spitzer Space Telescope. It was the second of the series to be launched into space, following the Hubble Space Telescope. CGRO was named after Arthur Holly Compton , Nobel prize winner, for work involved with gamma ray physics. CGRO was built by TRW in Redondo Beach, California. CGRO was an international collaboration and additional contributions came from the European Space Agency and various universities, as well as the U.S. Naval Research Laboratory.
CGRO carried a complement of four instruments that covered an unprecedented six decades of the electromagnetic spectrum, from 20 keV to 30 GeV . In order of increasing spectral energy coverage:
Gamma ray burst 990123 was one of the brightest bursts recorded at the time, and was the first GRB with an optical afterglow observed during the prompt gamma ray emission . This allowed astronomers to measure a redshift of 1.6 and a distance of 3.2 Gpc. Combining the measured energy of the burst in gamma-rays and the distance, the total emitted energy assuming an isotropic explosion could be deduced and resulted in the direct conversion of approximately two solar masses into energy. This finally convinced the community that GRB afterglows resulted from highly collimated explosions, which strongly reduced the needed energy budget.
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SPACE: NASA RECORD GAMMA RAY BURST
For the first time, astronomers have recorded visible light from the source of a gamma ray burst, an eruption more powerful than the energy of 10 (m) million (b) billion stars.
The images were captured by the Robotic Optical Transient Search Experiment (ROTSE) in New Mexico.
The gamma ray burst was detected on Saturday morning by two orbiting observatories.
News of the event was relayed through a network to astronomers. Ground-based telescopes were able to capture optical light from the fading afterglow that followed the 110-second peak of the burst.
Gamma ray bursts are common, happening several times a week. But they come and go so swiftly that astronomers have never before been able to link optical observations with the gamma ray detection.
Officials said the stellar eruption originated about 10 (b) billion light years away but was so powerful in visible light that it could have been sighted from the ground with binoculars if, by chance, someone had been looking.
The gamma ray burst phenomenon was discovered in 1967, but the bursts remain mysterious. They occur randomly across the sky several hundred times a year, with the peak of each burst lasting from a few milliseconds to a few minutes.
Astronomers do not know their origin or precise cause. Some speculate that bursts originate from black holes. Since gamma rays are invisible to the eye, the eruptions were unknown until the development of gamma ray detectors.
Saturday's burst was detected by NASA's Compton Gamma Ray Observatory and by the Italian-Dutch satellite BeppoSAX. Both satellite observatories regularly monitor the sky in search of such stellar events.
Based on the measured intensities of the light and the gamma rays, experts estimate energy released from the explosion could have been equal to the energy of 10 million (b) billion stars like the sun.
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USA/SPACE: NASA: COMPTON GAMMA RAY OBSERVATORY
It's a satellite many of us didn't even know existed, but to NASA, the information uncovered by the Compton Gamma Ray Observatory is priceless.
Despite this, NASA is set to send its successful mission to certain death on Sunday the 4th of June, in the name of public safety.
The Compton Gamma Ray Observatory was launched aboard the Space Shuttle Atlantis in April 1991.
For nine years, Compton has hovered in orbit, reliably scanning the galaxy for gamma rays.
Gamma rays are a powerful, yet invisible form of energy which can travel vast distances in space at the speed of light without being changed.
Astronomers believe these rays may hold clues to many things, including the processes involved in the creation of the elements.
"It tells us about things in the Cosmos where the most energetic things are going on: quasars, black holes, pulsars, high energy cosmic rays...Things that tend to be of high energy and high temperature."
SUPER CAPTION: Dr Alan Bunner, NASA Science Programme Director
During its nine years in space, Compton had tremendous successes.
In 1997, it thrilled scientists when it detected a blast of gamma rays that was 12 billion years old.
But, the observatory ran into problems last year, when one of the spacecraft's controlling devices - called a gyroscope - failed.
The craft needs two gyroscopes to operate, so the failure left the satellite with no backup, and NASA a little nervous.
"The gyroscopes are one of the devices that help keep the spacecraft stabilised. And that left us just one step away from not being able to do a controlled re-entry, and so we realised at that point that we had to scurry and find a way to safely and reliably bring GRO to ground."
SUPER CAPTION: Dr Alan Bunner, NASA Science Programme Director
Unlike most satellites, Compton is too large to burn up entirely in the atmosphere.
More than six tons of metal debris is expected to fall to the Earth's surface, ranging in size from tiny fragments to several hundred pounds.
To ensure public safety, NASA said it had no choice but to control the satellite's de-orbit, and make sure it crashes into an area void of human life.
"If we were to do nothing, if we had done nothing over the past several months, then we could face an uncontrolled re-entry, which means the spacecraft would begin to enter the atmosphere in a few years, it would begin to tumble as it gets buffeted by the upper-atmosphere, and then it would break apart, and where those pieces fell, nobody knows, nobody could say, and it could fall, in principle, on populated areas. That's the situation we have to avoid."
SUPER CAPTION: Dr. Alan Bunner, NASA Science Programme Director
Debris from the Compton Observatory is expected to fall in a remote area of the Pacific Ocean, approximately 25-hundred (2500) miles (approximately 1550 kilometres) southeast of Hawaii, and thousands of miles away from any land or life.
NASA says despite the death of one of its most successful satellites, Compton's task was too important to let die.
Doctor Bunner says there are at least four satellites preparing to be launched over the next few years that will pick up where the Compton Gamma Ray Observatory left off.
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USA/SPACE COMPTON GAMMA RAY OBSERVATORY DUMPED
NASA put on a big light show early on Sunday, but it's not yet sure whether there were any witnesses.
The space agency deliberately crashed a 17-ton satellite into a remote section of the Pacific Ocean.
The Compton orbiting observatory was launched in 1991.
The 670 (m) million dollar project was supposed to last two years, but was up and running for more than nine, providing a wealth of data for astronomers.
A failed gyroscope prompted the space agency to decide in March to dump the Compton.
Its 370-mile orbit would have kept it aloft for another 11 years, but NASA was worried that if more equipment failed engineers would not be able to control the vehicle and it would make a dangerous random return to Earth.
So early on Sunday, the observatory was lined up for a final, fiery plunge to the ocean as NASA set out to deliberately crash a satellite for the first time ever.
Engineers directed the Compton through a series of suicide rocket firings that dropped it from a high orbit and sent it plunging to Earth.
The 17-ton spacecraft worked perfectly through a final 30-minute rocket firing and then engineers watched on instruments in mission control as the speeding satellite heated, broke apart and then went silent.
The craft began coming apart about 0214 local time and engineers estimated that it would take as long as 20 minutes for some of the lighter pieces finally to hit the water.
An Air Force observation plane reported sighting pieces of the spacecraft falling toward the ocean.
It was estimated that about six tons of superheated metal survived the scorching re-entry and splashed in the Pacific.
The target was a corridor starting some 25-hundred miles southeast of Hawaii and extending for more than two-thousand miles toward the southeast.
Tracking signals from the spacecraft's final minutes indicated that its surviving pieces would safely hit the
target, far from any land.
Among the pieces predicted to survive re-entry and hit the ocean were six 18-hundred pound aluminum I-beams and parts made of titanium, including more than five-thousand bolts.
NASA engineers had calculated that if Compton was allowed to fall on its own, there was a chance of one in a thousand that someone would be killed.
A controlled re-entry dropped the odds of a fatality to about one in 29 (m) million.
The operation all apparently went smoothly.
\"...and I was honoured to support the mission as technical analyst, and from the centre directors' side, you made me proud, you all did a great job\"
SUPER CAPTION: Re-entry Controller
Compton was the first major space observatory to make a systematic survey of natural sources of gamma rays - an invisible ray that is the most energetic part of the electromagnetic spectrum.
In nine years of observations, Compton is said to have changed the way astronomers view the universe.
The craft detected more than 26-hundred gamma ray bursts and showed that they are occurring throughout the universe.
Astronomers have written about two-thousand papers based on data from Compton and more than 100 astronomers annually used the spacecraft to make observations.
Compton was the second of NASA's great, orbiting observatories - spacecraft that get a clear view of the universe above the obscuring effect of the atmosphere.
The other two, the Hubble Space Telescope and the Chandra X-ray Observatory, are still in orbit, working smoothly.
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Compton Gamma Ray Observatory
The Compton Gamma ray observatory
The Compton Gamma ray observatory was a space telescope made by NASA to identify gamma rays. All information in the video
Hubble, Compton Gamma Ray, Chandra X-Ray, Spitzer: "The Four Great Observatories" NASA
more at http://scitech.quickfound.net/
"This video presentation introduces the Hubble Space Telescope, Gamma Ray Observatory, Advanced X-ray Astrophysics Facility (AXAF), and the Shuttle Infrared Telescope Facility (SIRTF). This film is cataloged as NASA-TM-109311."
Public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
The Hubble Space Telescope (HST) is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4-meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble.
Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely sharp images with almost no background light. Hubble's Deep Fields have been some of the most detailed visible-light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe...
The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope...
The telescope is now expected to function until at least 2013. Its scientific successor, the James Webb Space Telescope (JWST), is to be launched in 2018 or possibly later...
The Compton Gamma Ray Observatory (CGRO) was a space observatory detecting light from 20 KeV to 30 GeV in Earth orbit from 1991 to 2000. It featured four main telescopes in one spacecraft covering x-rays and gamma-rays, including various specialized sub-instruments and detectors. Following 14 years of effort, the observatory was launched on the Space Shuttle Atlantis, mission STS-37, on 5 April 1991 and operated until its deorbit on 4 June 2000. It was deployed in low earth orbit at 450 km (280 mi) to avoid the Van Allen radiation belt. It was the heaviest astrophysical payload ever flown at that time at 17,000 kilograms (37,000 lb)...
CGRO was named after Dr. Arthur Holly Compton (Washington University in St. Louis), Nobel prize winner, for work involved with gamma ray physics. CGRO was built by TRW (now Northrop Grumman Aerospace Systems) in Redondo Beach, CA. CRGO was an international collaboration and additional contributions came from the European Space Agency and various Universities, as well as the U.S. Naval Research Laboratory...
The Chandra X-ray Observatory is a space telescope launched on STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, enabled by the high angular resolution of its mirrors. Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes; therefore space-based telescopes are required to make these observations. Chandra is an Earth satellite in a 64 hour orbit, and its mission is ongoing as of 2013.
Chandra is one of the Great Observatories, along with the Hubble Space Telescope, Compton Gamma Ray Observatory (1991-2000), and the Spitzer Space Telescope. Chandra has been described as being as revolutionary to astronomy as Galileo's first telescope.
It was named in honor of the Nobel-prize winning Indian-American astrophysicist Subrahmanyan Chandrasekhar who worked for University of Chicago from 1937 until he died in 1995. He was known for determining the maximum mass for white dwarfs...
The Spitzer Space Telescope (SST), formerly the Space Infrared Telescope Facility (SIRTF) is an infrared space observatory launched in 2003. It is the fourth and final of the NASA Great Observatories program.
The planned mission period was to be 2.5 years with a pre-launch expectation that the mission could extend to five or slightly more years until the onboard liquid helium supply was exhausted. This occurred on 15 May 2009. Without liquid helium to cool the telescope to the very cold temperatures needed to operate, most instruments are no longer usable. However, the two shortest wavelength modules of the IRAC camera are still operable with the same sensitivity as before the cryogen was exhausted, and will continue to be used in the Spitzer Warm Mission...
Space Shuttle STS-37 Atlantis Compton Gamma Ray Observatory pt2-2 Post Flight Press 1991 NASA
more at http://scitech.quickfound.net/astro/space_shuttle_news.html
Public domain film slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and equalization (the resulting sound, though not perfect, is far less noisy than the original).
Split with MKVmerge GUI (part of MKVToolNix), the same freeware (or Avidemux) can recombine the downloaded parts (in mp4 format): http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge-gui.html
part 1: had to be deleted due to a bogus copyright claim
STS-37, the eighth flight of the Space Shuttle Atlantis, was a six-day mission with the primary objective of launching the Compton Gamma Ray Observatory (GRO), the second of the Great Observatories program which included the visible-spectrum Hubble Space Telescope, the Chandra X-ray Observatory and the infrared Spitzer Space Telescope. The mission also featured two spacewalks, the first since 1985.
Commander Steven R. Nagel Third spaceflight
Pilot Kenneth D. Cameron First spaceflight
Mission Specialist 1 Jerry L. Ross Third spaceflight
Mission Specialist 2 Jay Apt First spaceflight
Mission Specialist 3 Linda M. Godwin First spaceflight
he STS-37 mission was successfully launched from launch pad 39B at 9:22:44AM EST on April 5, 1991 from the Kennedy Space Center in Florida...
The primary payload, Gamma Ray Observatory (GRO), was deployed on flight day 3. GRO's high-gain antenna failed to deploy on command; it was finally freed and manually deployed by Ross and Apt during an unscheduled contingency space walk, the first since April 1985. The following day, the two astronauts performed first scheduled space walk since November 1985 to test means for astronauts to move themselves and equipment about while maintaining the then-planned Space Station Freedom. GRO science instruments were Burst and Transient Source Experiment (BATSE), Imaging Compton Telescope (COMPTEL), Energetic Gamma Ray Experiment Telescope (EGRET) and Oriented Scintillation Spectrometer Experiment (OSSE). GRO was the second of NASA's four Great Observatories. The Hubble Space Telescope, deployed during Mission STS-31 in April 1990, was the first. GRO was launched on a two-year mission to search for the high-energy celestial gamma ray emissions, which cannot penetrate Earth's atmosphere. At about 35,000 pounds, GRO was the heaviest satellite to be deployed into low-Earth orbit from the Shuttle. It was also designed to be the first satellite that could be refueled in orbit by Shuttle crews. Five months after deployment, NASA renamed the satellite the Arthur Holly Compton Gamma Ray Observatory, or Compton Observatory, after the Nobel Prize-winning physicist who did important work in gamma ray astronomy.
The first U.S. extravehicular activity (EVA) or spacewalk since 1985 was performed by Mission Specialists Jerry L. Ross and Jay Apt after six failed attempts to deploy the satellite's high-gain antenna. Repeated commands by ground controllers at the Payload Operations Control Center, Goddard Space Flight Center, Greenbelt, MD, and maneuvering of Atlantis and its Remote Manipulator System (RMS) robot arm, as well as GRO's antenna dish, were to no avail in dislodging the boom. Ross and Apt were prepared for such a contingency, and Ross freed the antenna boom within 17 minutes after beginning the spacewalk. It was the first unscheduled contingency EVA since STS-51-D in April 1985. Deployment occurred about 18:35 EST, approximately 41⁄2 hours after it was scheduled.
The following day, on 8 April 1991, Ross and Apt made the first scheduled EVA since Mission STS-61-B in November 1985. The spacewalk was to test methods of moving crew members and equipment around the future Space Station Freedom. One of the experiments was to evaluate manual, mechanical and electrical power methods of moving carts around the outside of large structures in space. Although all three methods worked, the astronauts reported that propelling the cart manually or hand-over-hand worked best. With both EVAs, Ross and Apt logged 10 hours and 49 minutes walking in space during STS-37. Crew members also reported success with secondary experiments.
During one of the EVAs, a small rod from within the spacesuit punctured the seal of one of the astronauts' gloves (the name is undisclosed, but it was either Ross or Apt). However, the astronaut's hand partially sealed the hole, resulting in no detectable depressurization. In fact, the puncture was not noticed until after the spacewalkers were safely back inside Atlantis...
11 April 1991, 06:55:29 PDT, Runway 33, Edwards Air Force Base, CA. Rollout distance: 6,364 feet. Rollout time: 56 seconds...
Gamma-Ray Spectra Part One
1991: STS-37 Atlantis, Gamma Ray Observatory (NASA)
Space Shuttle flight 39 (STS-37), launched on 5 April 1991 and narrated by the astronauts. Crew: Steven R. Nagel, Kenneth D. Cameron, Jerry L. Ross, Jay Apt, Linda M. Godwin.
NASA's Swift Catches 500th Gamma-ray Burst
In its first five years in orbit, NASA's Swift satellite has given astronomers more than they could have hoped for. Its discoveries range from a nearby nascent supernova to a blast so far away that it happened when our universe was only 5 percent of its present age.
Swift primarily studies gamma-ray bursts (GRBs) -- the biggest and most mysterious explosions in the cosmos. On April 13, the spacecraft's "burst-o-meter" cataloged its 500th GRB.
"On the one hand, it's just a number, but on the other it is a remarkable milestone," said Neil Gehrels, Swift's lead researcher at Goddard Space Flight Center in Greenbelt, Md. "Each burst has turned over a new piece of the puzzle and a clearer picture is emerging."
"Over five years and 500 bursts, Swift has fulfilled every significant promise of its mission and, in addition, brought a wealth of surprises," noted Derek Fox, a Swift team member at Penn State in University Park, Pa.
Burst 500, officially known as GRB 100413B, exploded in constellation Cassiopeia as a long burst, a type usually associated with the death of a massive star. It wasn't detected in on-board analysis of data from the spacecraft's Burst Alert Telescope (BAT), which was interrupted 18 seconds after the burst as Swift slewed to a pre-planned target.
Instead, GRB 100413B came to light when David Palmer, an astrophysicist at Los Alamos National Laboratory in New Mexico, later analyzed the data. "The BAT team regularly digs through the data once it comes to the ground and finds weak bursts like this one that take a bit of special care," said Goddard's Judith Racusin, who coordinated burst observations that day.
Summaries of other notable bursts in Swift's storied career are listed below.
Swift's main job is to quickly localize each gamma-ray burst, report its position so that others can immediately conduct follow-up observations, and then study the burst using its X-ray and Ultraviolet/Optical telescopes. But it does much more, including ultraviolet studies of exploding stars, monitoring black holes and neutron stars for surges of high-energy radiation, and carrying out a long-term X-ray survey of the entire sky.
The spacecraft rocketed into orbit in November 2004. Managed by NASA's Goddard Space Flight Center, Swift was built and is operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and General Dynamics of Gilbert, Ariz. Other partners include the University of Leicester and Mullard Space Science Laboratory in the United Kingdom, Brera Observatory and the Italian Space Agency in Italy, with additional collaborators in Germany and Japan.
Because gamma rays are the highest-energy form of light, the brief but brilliant blasts represent a colossal energy release. Gamma-ray bursts were discovered in 1967 by unclassified military satellites designed to look for clandestine nuclear tests. The first observations required extensive analysis to be sure that the bursts were truly originating beyond the solar system, and they weren't published until 1973.
Over the following years, astronomers learned that sufficiently sensitive instruments could detect about two bursts per day, on average, somewhere in the sky. Of those twice-daily GRBs, Swift's Burst Alert Telescope snares about one in eight for detailed study.
According to Lorella Angelini, a Goddard astrophysicist now developing a comprehensive burst database, the number of recorded GRBs is approaching 6,000. Yet if one considers only bursts with measured distances, Swift's share of the total is a whopping 75 percent.
An earlier NASA satellite, the Compton Gamma Ray Observatory, showed that bursts come in long and short varieties, with long bursts (those lasting longer than two seconds) outnumbering short bursts three to one. Compton also showed that bursts occur randomly and evenly over the sky. Maps of GRB distribution bear no hint of our galaxy's structure. This means that they are extremely far away — and all the more powerful.
INAF press release
Penn State release
Sonoma State University's real-time GRB sky map
NASA Scientists Catch a Unique Gamma-Ray Burst (GRB 050509b)
Scientists Detect New Kind of Cosmic Explosion (GRB 060218)
"Naked-Eye" Gamma-Ray Burst Was Aimed Squarely At Earth (GRB080319B)
New Gamma-Ray Burst Smashes Cosmic Distance Record (GRB 090423)
NASA's Swift Catches 500th Gamma-ray Burst
NASA's Three Great Observatories
The Chandra X-ray Observatory is one of NASA's "Great Observatories," along with the Hubble Space Telescope, the Spitzer Space Telescope, and the Compton Gamma Ray Observatory (now de-orbited). Chandra gives astronomers the power to investigate X-rays across the universe. This animation shows a short segment of each of the three active Great Observatories (Chandra, Hubble, and Spitzer) as depicted in their orbits.
(Credit: Chandra: NASA/CXC/A.Hobart; Hubble: NASA/ESA/STScI/G.Bacon; Spitzer: NASA/JPL)