NASA Space Telescopes Capture the Biggest, Baddest Gamma Ray Blast Ever Seen
Gamma-ray bursts (GRBs) are the most luminous and powerful explosions in the Universe, thought to be triggered when the core of a massive star runs out of nuclear fuel, collapses under its own weight, and forms a black hole. The black hole then drives jets of particles that drill all the way through the collapsing star and erupt into space at nearly the speed of light. NASA’s Hubble Space Telescope has given astronomers a peek at the location of the most energetic outburst ever seen in the Universe – a Gamma Ray Burst that in a few seconds emitted more energy than the Sun will provide over its entire 10 billion year life. As shown in this illustration of Gamma Ray Burst GRB 190114C, Hubble’s observations suggest that this particular burst displayed such powerful emission because the collapsing star was sitting in a very dense environment, right in the middle of a bright galaxy 5 billion light years away. (Image Credit: NASA, ESA, and M. Kornmesser)
NASA Space Telescopes Capture the Biggest, Baddest Gamma Ray Blast Ever Seen
Gamma Ray Bursts (GRBs) were discovered by American surveillance satellites in the late 1960s. These satellites were looking for gamma rays coming from possible clandestine Soviet nuclear tests. Instead these satellites found brief but intense flashes of gamma rays coming from random directions in space. To this day GRBs remain one of the greatest mysteries of modern astronomy. Despite lasting only a few milliseconds to several minutes, they are the most energetic phenomena known. An individual GRB can release in a matter of seconds the same amount of energy that our Sun will radiate over its 10 billion year lifetime.
In January 2019, an extremely bright and long-duration GRB was detected by a suite of telescopes including NASA’s space-based Swift and Fermi telescopes, as well as by the land-based Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes on the Canary Islands. Follow-up observations were made with Hubble to study the environment around the GRB to find out how this extreme emission was produced.
“Hubble’s observations suggest that this particular burst was sitting in a very dense environment, right in the middle of a bright galaxy 5 billion light years away. This is really unusual, and suggests that this concentrated location might be why it produced this exceptionally powerful light,” explained Andrew Levan of the Institute for Mathematics, Astrophysics, and Particle Physics Department of Astrophysics at Radboud University in the Netherlands.
“Scientists have been trying to observe very high energy emission from Gamma Ray Bursts for a long time,” explained Antonio de Ugarte Postigo of the Instituto de Astrofisica de Andalucia in Spain. "This new Hubble observation of accompanying lower-energy radiation from the region is a vital step in our understanding of Gamma Ray Bursts [and] their immediate surroundings."
The complementary Hubble observations reveal that the GRB occurred within the central region of a massive galaxy. Researchers say that this is a denser environment than typically observed [for GRBs] and could have been crucial for the generation of the very high energy radiation that was observed. The host galaxy of the GRB is actually one of a pair of colliding galaxies. The galaxy interactions may have contributed to spawning the outburst.
Known as GRB 190114C, some of the radiation detected from the object had the highest energy ever observed. Scientists have been trying to observe such very high energy emission from GRBs for a long time, so this detection is considered a milestone in high-energy astrophysics, say the researchers.
Previous observations revealed that to achieve this energy, material must be emitted from a collapsing star at 99.999 percent the speed of light. This material is then forced through the gas that surrounds the star, causing a shock that creates the Gamma Ray Burst itself.
Previous record for a GRB was in 2013
Gamma rays are the most energetic form of light. Hot matter surrounding a new black hole and internal shock waves produced by collisions within the jet are thought to emit gamma rays with energies in the million electron-volt (MeV) range, or roughly 500,000 times the energy of visible light. The most energetic emission, with billion electron-volt (GeV) gamma rays, is thought to arise when the jet slams into its surroundings, forming an external shock wave.
On April 27, 2013 a blast from a dying star in a distant galaxy became the focus of astronomers around the world. The Gamma Ray Burst designated GRB 130427A, topped the charts as the brightest ever seen.
As luck would have it, a trio of NASA satellites, working in concert with ground based robotic telescopes, captured never before seen details of the event that have been used to challenge current theoretical understandings of how Gamma Ray Bursts work.
The Gamma-ray Burst Monitor (GBM) aboard NASA's Fermi Gamma Ray Space Telescope captured the initial wave of gamma rays from GRB 130427A shortly after 3:47 AM EDT on April 27th. In its first three seconds alone, the "monster burst" proved brighter than almost any burst previously observed.
"We expect to see an event like this only once or twice a century, so we're fortunate it happened when we had the appropriate collection of sensitive space telescopes with complementary capabilities available to see it," said Paul Hertz, director of NASA's Astrophysics Division in Washington.
"The spectacular results from Fermi GBM show that our widely accepted picture of MeV gamma rays from internal shock waves is woefully inadequate," said Rob Preece, a Fermi team member at the University of Alabama in Huntsville who led the GBM study.
NASA's Swift Gamma-ray Burst Mission detected the burst almost simultaneously with the GBM and quickly relayed its position to ground based observatories.
Telescopes operated by Los Alamos National Laboratory in New Mexico as part of the Rapid Telescopes for Optical Response (RAPTOR) Project quickly turned to the spot. They detected an optical flash that peaked at magnitude 7 on the astronomical brightness scale, easily visible through binoculars. It is the second brightest flash ever seen from a Gamma Ray Burst.
Just as the optical flash peaked, Fermi's Large Area Telescope (LAT) detected a spike in GeV gamma rays reaching 95 GeV, the most energetic light ever seen from a burst. This relationship between a burst's optical light and its high-energy gamma-rays defied expectations.
"We thought the visible light for these flashes came from internal shocks, but this burst shows that it must come from the external shock, which produces the most energetic gamma rays," said Sylvia Zhu, a Fermi team member at the University of Maryland.
The LAT detected GRB 130427A for about 20 hours, far longer than any previous burst. For a gamma ray burst, it was relatively nearby. Its light traveled 3.8 billion years before arriving at Earth, about one third the travel time for light from typical bursts.
"Detailed observations by Swift and ground-based telescopes clearly show that GRB 130427A has properties more similar to typical distant bursts than to nearby ones," said Gianpiero Tagliaferri, a Swift team member at Brera Observatory in Merate, Italy.
This extraordinary event enabled NASA's newest X-ray observatory, the Nuclear Spectroscopic Telescope Array (NuSTAR), to make a first time detection of a burst afterglow in high energy, or "hard," X-rays after more than a day. Taken together with Fermi LAT data, these observations challenged long-standing predictions.
"We have waited a long time for a gamma-ray burst this shockingly, eye-wateringly bright," said Julie McEnery, project scientist for the Fermi Gamma Ray Space Telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The GRB lasted so long that a record number of telescopes on the ground were able to catch it while space-based observations were still ongoing."
Fermi's Large Area Telescope (LAT) recorded one gamma ray with an energy of at least 94 billion electron volts (GeV), or some 35 billion times the energy of visible light, and about three times greater than the LAT's previous record. The GeV emission from the burst lasted for hours, and it remained detectable by the LAT for the better part of a day, setting a new record for the longest gamma-ray emission from a GRB.
The burst subsequently was detected in optical, infrared and radio wavelengths by ground-based observatories, based on the rapid accurate position from Swift. Astronomers quickly learned that the GRB was located about 3.6 billion light-years away, which for these events is relatively close.
A GRB captured by NASA’s Fermi in September 2008 was also one for the record books
The first Gamma Ray Burst (GRB) to be seen in high-resolution from NASA's Fermi Gamma Ray Space Telescope was one for the record books. At the time, the blast had the greatest total energy, the fastest motions, and the highest-energy initial emissions ever seen.
"We were waiting for this one," said Peter Michelson, the principal investigator on Fermi's Large Area Telescope at Stanford University. "Burst emissions at these energies are still poorly understood, and Fermi is giving us the tools to understand them."
Gamma Ray Bursts are the universe's most luminous explosions. Astronomers believe most occur when exotic massive stars run out of nuclear fuel. As a star's core collapses into a black hole, jets of material -- powered by processes not yet fully understood -- blast outward at nearly the speed of light. The jets bore all the way through the collapsing star and continue into space, where they interact with gas previously shed by the star and generate bright afterglows that fade with time.
This explosion, designated GRB 080916C, occurred at 7:13 p.m. EDT on Sept. 15, 2008 in the constellation Carina. Fermi's other instrument, the Gamma Ray Burst Monitor, simultaneously recorded the event. Together, the two instruments provided a view of the blast's initial gamma ray emission from energies between 3000 to more than 5 billion times that of visible light.
Nearly 32 hours after the blast, Jochen Greiner of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, led a group that searched for the explosion's fading afterglow. The team simultaneously captured the field in seven wavelengths using the Gamma Ray Burst Optical/Near-Infrared Detector, or GROND, on the 2.2-meter telescope at the European Southern Observatory in La Silla, Chile. In certain colors, the brightness of a distant object shows a characteristic drop-off caused by intervening gas clouds. The farther away the object is, the redder the wavelength where this fade-out occurs. This gave astronomers a quick estimate of the object's distance. The team's follow-up observations established that the explosion took place 12.2 billion light-years away.
"Already, this was an exciting burst," said Julie McEnery, a Fermi deputy project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "But with the GROND team's distance, it went from exciting to extraordinary."
With the distance in hand, Fermi team members showed that the blast exceeded the power of approximately 9000 ordinary supernovae, if the energy was emitted equally in all directions. This is a standard way for astronomers to compare events even though gamma-ray bursts emit most of their energy in tight jets.
Coupled with the Fermi measurements, the distance also helped astronomers determine the slowest speeds possible for material emitting the prompt Gamma Rays. Within the jet of this burst, gas bullets must have moved at 99.9999 percent the speed of light. This burst's tremendous power and speed made it the most extreme recorded to date.
One curious aspect of the burst was a five second delay separating the highest energy emissions from the lowest. Such a time lag had been seen clearly in only one earlier burst.
"It may mean that the highest energy emissions are coming from different parts of the jet or created through a different mechanism," Michelson said.
A GRB detected in March 2008 by NASA's Swift shattered the record for the most distant object ever seen with the naked eye
Astronomers are familiar with seeing amazing things through their telescopes. But nothing prepared them for an incredible explosion detected in the early morning of March 19, 2008 by NASA’s Swift satellite. At 2:12 a.m. EDT, Swift detected an explosion from deep space that was so powerful that its afterglow was briefly visible to the naked eye. Even more astonishing, the explosion itself took place halfway across the visible universe.
Never before had anything so far away come even close to naked eye visibility. The explosion was so far away that it took its light 7.5 billion years to reach Earth. In fact, the explosion took place so long ago that Earth had not yet come into existence.
"This burst was a whopper," said Swift principal investigator Neil Gehrels of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It blows away every gamma ray burst we've seen so far."
Swift's Burst Alert Telescope picked up the burst at 2:12 a.m. EDT on March 19th, and pinpointed the coordinates in the constellation Bootes. Telescopes in space and on the ground quickly moved to observe the afterglow. The burst was named GRB 080319B. (The “B” designation indicated that it was the second gamma ray burst detected that day).
Swift's other two instruments, the X-ray Telescope and the Ultraviolet/Optical Telescope, also observed brilliant afterglows. Several ground-based telescopes saw the afterglow brighten to visual magnitudes between 5 and 6 in the logarithmic magnitude scale used by astronomers. (The brighter an object is, the lower its magnitude number). From a dark location in the countryside, people with normal vision can see stars slightly fainter than magnitude 6. That means the afterglow would have been dim, but visible to the naked eye.
Later that evening, the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst's redshift at 0.94. A redshift is a measure of the distance to an object. A redshift of 0.94 translates into a distance of 7.5 billion light years, meaning the explosion took place 7.5 billion years ago, a time when the Universe was less than half its current age and Earth had not yet formed. This is more than halfway across the visible Universe.
"No other known object or type of explosion could be seen by the naked eye at such an immense distance," said Swift science team member Stephen Holland of Goddard. "If someone just happened to be looking at the right place at the right time, they saw the most distant object ever seen by human eyes without optical aid."
GRB 080319B's optical afterglow was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. The most distant previous object that could have been seen by the naked eye is the nearby galaxy M33, at a relatively short 2.9 million light years from Earth.
Astronomers don't know why this burst and its afterglow were so bright. One possibility is the burst was more energetic than others, perhaps because of the mass, spin, or magnetic field of the progenitor star or its jet. Or perhaps it concentrated its energy in a narrow jet that was aimed directly at Earth.
Wolf-Rayet 104 has us locked in its gunsights -- Are we in danger of a GRB-driven Extinction Level Event?
Fears about global warming and climatic changes are child's play compared to what Wolf-Rayet 104 (WR 104) may have in store for us. WR 104 is now in the last known stable phase for a massive star of this type and is only about 8000 light years away. The problem is that its polar orientation appears to be "face-on" to Earth's line of sight. Essentially, we are staring right down a gun barrel. If WR 104 collapses into a Supernova (as expected) and releases a Gamma Ray Burst, our Solar System could be in the direct path of a highly collimated jet of destruction and such an event could end life as we know it.
But will it happen in the next thousand years or in the next 500,000 years? Nobody knows... And nobody can do anything about it because the GRB and bright light from the Supernova would arrive here simultaneously. Our only hope is that a few degrees one way or the other in the orientation of WR 104 could make all the difference in the world.
It is believed that this would not be the first time a GRB caused an Extinction Level Event (ELE) here on Earth. Scientists at NASA and the University of Kansas say that a mass extinction on Earth hundreds of millions of years ago could have been triggered by a GRB, but the scientists do not have direct evidence that such a burst activated this ancient extinction. The strength of their work is in their atmospheric modeling -- essentially a "what if" scenario.
The scientists calculated that gamma ray radiation from a relatively nearby star explosion, hitting the Earth for only ten seconds, could deplete up to half of the atmosphere's protective Ozone layer. Recovery of the Ozone layer would take at least five years. However, with the Ozone layer damaged, Ultraviolet (UV) radiation from the Sun could kill-off much of the life on land and near the surface of oceans and lakes. That in itself would constitute an Extinction Level Event. But the real long term killer would be the disruption of the food chain.
GRBs in our Milky Way galaxy are indeed rare, but scientists estimate that at least one nearby GRB likely hit the Earth in the past billion years.
"A Gamma Ray Burst originating within 6000 light years from Earth would have a devastating effect on life," according to Dr. Adrian Melott of the Department of Physics and Astronomy at the University of Kansas. "We don't know exactly when one came, but we're rather sure it did come and left its mark. What's most surprising is that just a 10 second burst can cause years of devastating Ozone damage."
GRBs are the most powerful explosions known. Most originate in distant galaxies and a large percentage likely arise from explosions of stars over 15 times more massive than our Sun. A burst creates two oppositely directed and highly collimated beams of gamma rays that race off into space.
Brian Thomas of University of Kansas says that a Gamma Ray Burst may have caused the Ordovician extinction 450 million years ago, killing 60 percent of all marine invertebrates. At that time, life was largely confined to the sea, although there is evidence of primitive land plants during this period. To put things in relative perspective, the Ordovician extinction was about 200 million years before the time of the dinosaurs. The first life on Earth is thought to have appeared about 3.5 billion years ago.
In their work, the team used detailed computer models to calculate the effects of a nearby Gamma Ray Burst on the atmosphere and the consequences for life.
Thomas, with Dr. Charles Jackman of NASA's Goddard Space Flight Center in Greenbelt, Maryland, calculated the effect of a nearby GRB on the Earth's atmosphere. Gamma rays, a high energy form of light, can break molecular Nitrogen (N2) into Nitrogen atoms, which react with molecular Oxygen (O2) to form Nitric Oxide (NO). NO will destroy Ozone (O3) and produce Nitrogen Dioxide (NO2). NO2 would then react with atomic Oxygen to reform NO. More NO means more Ozone destruction. Computer models show that up to half the Ozone layer would be destroyed within weeks. Five years on, some of the Ozone would reform, but at least 10 percent would remain destroyed.
Next Thomas and Daniel Hogan, also of the University of Kansas, calculated the effect of UV radiation on life. Deep sea creatures living several feet below water would be protected. Surface dwelling plankton and other life near the surface, however, would not survive. This would be a major problem, as Plankton is the foundation of the marine food chain.
Dr. Bruce Lieberman, a paleontologist at the University of Kansas, originated the idea that a Gamma Ray Burst specifically could have caused the great Ordovician extinction 200 million years before the dinosaurs. An ice age is thought to have caused this extinction. But a Gamma Ray Burst could have caused a fast die-out early on and also could have triggered the significant drop in surface temperature on Earth.
"One unknown variable is the rate of local Gamma Ray Bursts," said Thomas. "The bursts we detect today originated far away billions of years ago, before the Earth formed. Among the billions of stars in our Galaxy, there's a good chance that a massive one relatively nearby exploded and sent gamma rays our way."
But Don’t Worry – A deadly nearby Gamma Ray Burst is highly unlikely
Some scientists have wondered whether a deadly Gamma Ray Burst could happen in a galaxy like ours, but a group of astronomers at Ohio State University (OSU) and their colleagues determined in 2006 that such an event would be nearly impossible.
Gamma ray bursts are high energy beams of radiation that shoot out from the north and south magnetic poles of a particular kind of star during a supernova explosion, explained Krzysztof Stanek, Associate Professor of Astronomy at OSU. Scientists suspect that if a GRB were to occur near our Solar System and one of the beams were to hit Earth, it could cause mass extinctions all over the planet.
The GRB would have to be less than 3000 light years away to pose a danger, Stanek said. One light year is approximately 6 trillion miles, and our galaxy measures 100,000 light years across. So the event would not only have to occur in our galaxy, but relatively close by as well.
In the study, Stanek and his team found that GRBs tend to occur in small, misshapen galaxies that lack heavy chemical elements (astronomers often refer to all elements other than the very lightest ones -- hydrogen, helium, and lithium -- as metals). Even among metal-poor galaxies, the events are rare.
But the Milky Way is different from these GRB galaxies on all counts -- it's a large spiral galaxy with lots of heavy elements.
The astronomers did a statistical analysis of four GRBs that happened in nearby galaxies, explained Oleg Gnedin, a postdoctoral researcher at OSU. They compared the mass of the four host galaxies, the rate at which new stars were forming in them, and their metal content to other galaxies catalogued in the Sloan Digital Sky Survey (SDSS).
Though four may sound like a small sample compared to the number of galaxies in the universe, these four were the best choice for the study because astronomers had data on their composition, Stanek said. All four were small galaxies with high rates of star formation and low metal content.
Of the four galaxies, the one with the most metals -- the one most similar to ours -- hosted the weakest GRB. The astronomers determined that the odds of a GRB occurring in a galaxy like that one to be approximately 0.15 percent.
And the Milky Way's metal content is twice as high as that galaxy, so our odds of ever having a GRB would be even lower than 0.15 percent.
"We didn't bother to compute the odds for our galaxy, because 0.15 percent seemed low enough," Stanek said.
He figures that most people weren't losing sleep over the possibility of an Earth-annihilating GRB. "I wouldn't expect the stock market to go up as a result of this news, either," he said. "But there are a lot of people who have wondered whether GRBs could be blamed for mass extinctions early in Earth's history, and our work suggests that this is not the case."
Astronomers have studied GRBs for more than 50 years, and only recently determined where they come from. In fact, Stanek led the team that tied GRBs to supernovae in 2003.
He and Gnedin explained that when a very massive, rapidly rotating star explodes in a supernova, its magnetic field directs gamma radiation to flow only out of the star's north and south magnetic poles, forming high intensity jets.
Scientists have measured the energies of these events and assumed -- rightly so, Stanek said -- that such high intensity radiation could destroy life on a planet. That's why some scientists have proposed that a GRB could have been responsible for a mass extinction that occurred on Earth 450 million years ago.
Now it seems that gamma ray bursts may not pose as much a danger to Earth or any other potential life in the universe, either, since they are unlikely to occur where life would develop.
Planets need metals to form, Stanek said, so a low metal galaxy would probably have fewer planets, and fewer chances for life.
"My initial reaction was that it's not a coincidence, and everyone just knows that GRBs happen in metal-poor galaxies. But then people asked, 'Is it really that well known? Has anybody actually proven it to be true?' And we realized that nobody had."
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