- 3184 - GAMMA RAY BURSTS - caused by exploding stars? GRBs are short-lived bursts of gamma-ray light, the most energetic form of light. Lasting anywhere from a few milliseconds to several minutes, GRBs shine hundreds of times brighter than a typical supernova and about a million trillion times as bright as the Sun.
- ---------- 3184 - GAMMA RAY BURSTS - caused by exploding stars?
- When a GRB erupts, it is briefly the brightest source of cosmic high-frequency gamma-ray photons in the observable Universe.
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- GRBs were arguably the biggest mystery in high-energy astronomy. They were discovered in the late 1960s by U.S. military satellites which were on the lookout for Soviet nuclear testing in violation of the atmospheric nuclear test ban treaty.
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- These satellites carried gamma ray detectors since a nuclear explosion produces gamma rays. They didn't find any violations of the nuclear treaty, but they did discover bright bursts of gamma rays from beyond the solar system.
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- Evidence from recent satellites like Swift and Fermi indicate that the energy behind a gamma-ray burst comes from the collapse of matter into a blackhole. When astronomers looked at the number of bursts versus how long they lasted, they found two different classes of bursts: long-duration and short-duration. These two classes are likely created by different processes, but the end result in both cases is a brand new blackhole.
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- Long-duration bursts last anywhere from 2 seconds to a few hundreds of seconds (several minutes), with an average time of about 30 seconds. They are associated with the deaths of massive stars in supernovas; though not every supernova produces a gamma-ray burst.
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- Short duration bursts are those that last less then 2 seconds; lasting anywhere from a few milliseconds to 2 seconds with an average duration of about 0.3 seconds (or 300 milliseconds). These bursts appear to be associated with the merger of two neutron stars into a new blackhole or a neutron star with a black hole to form a larger black hole.
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- These explosions occur when a massive star, five or 10 times the mass of our sun, detonates, abruptly becoming a blackhole.
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- Gamma-ray bursts may also occur when two superdense stellar corpses called neutron stars collide, often forming a blackhole. A gamma-ray burst that scientists watched during a few nights in 2019 likely occurred only about 1 billion light-years away from Earth, relatively close by for these dramatic events.
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- Two NASA space-based observatories, Fermi and Swift, first detected the event, which is known as GRB 190829A because it was detected on Aug. 29, 2019. The explosion came from the direction of the constellation Eridanus, a large swath of sky in the Southern Hemisphere.
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- When the scientists behind the new research heard about the gamma-ray burst detection, they mobilized a set of five gamma-ray telescopes in Namibia, called the High Energy Stereoscopic System (HESS). Over three nights, the telescopes observed the explosion for a total of 13 hours, in an attempt to understand what took place.
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- With those observations, the scientists could analyze much higher-energy photons than is possible in most distant gamma-ray bursts. The very-high-energy photons were not absorbed in collisions with background light on their way to Earth, as happens over larger distances in the cosmos.
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- During those analyses, the team noticed that the patterns of X-rays and very high-energy gamma-rays matched, something scientists wouldn't expect, since they believe different phenomena cause the two different types of radiation.
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- So far, 2021, scientists have only observed four of these bright explosions from the surface of Earth, so they're hoping that new instruments and additional observations give them more insight into the details of gamma-ray bursts
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- Gamma-ray bursts are the strongest and brightest explosions in the universe, thought to be generated during the formation of blackholes. Though they last mere seconds, gamma-ray bursts produce as much energy as the sun will emit during its entire 10-billion-year existence.
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- The mysterious phenomena were first seen in 1967 by a U.S. Air Force satellite called Vela. The probe was designed to keep watch for secret Soviet nuclear testing, but it ended up spotting dazzling gamma-rays coming from beyond the solar system. When such an event happened, it would briefly become the brightest gamma-ray object in the observable universe.
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- It wasn't until 1991 that astronomers launched the “Compton Gamma Ray Observatory” with the “Burst and Transient Source Experiment” (BATSE), which discovered roughly one new gamma-ray burst per day.
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- BATSE found that gamma-ray bursts were distributed evenly across the sky, meaning they were occurring everywhere in the universe. BATSE also showed that there were two types of gamma-ray bursts with distinct signatures: those that lasted 2 to 30 seconds, and those that flashed for less than 2 seconds.
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- Researchers have learned a great deal more about gamma-ray bursts by developing a network of rapid-response satellites and ground-based observatories that all converge on a gamma-ray burst as soon as it's detected.
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- This network has provided data showing that gamma-ray bursts are located in galaxies billions of light-years away and that, after the initial gamma-ray flare, the source of the burst produces an afterglow in less-energetic wavelengths.
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- The longer-lived versions of gamma-ray bursts have been found to be associated with ultrapowerful supernovas called “hyper novas“, which occur when stars between five and 10 times the mass of our sun end their lives and implode into blackholes
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- Hypernovas are 100 times brighter than typical supernovas and are thought to be generated by stars that are spinning particularly fast or have an especially strong magnetic field, imparting extra energy to their combustions.
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- These short-lived gamma-ray bursts, which make up 30% of such events, remained a mystery until 2005, mainly because they are too quick and fleeting for follow-up observations.
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- After being launched in 2004, the “Neil Gehrels Swift Observatory” (previously called the Swift Gamma-Ray Burst Explorer) was finally able to record enough data to see the afterglow of short-lived gamma-ray bursts and figure out that they were likely caused when two ultradense stellar corpses known as neutron stars collided and formed a blackhole, or when a blackhole ate a neutron star.
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- Such outbursts are so strong that they produce ripples in the fabric of space-time called “gravitational waves“. The “Laser Interferometer Gravitational-Wave Observatory” (LIGO), can detect gravitational waves from these collisions.
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- There are still many unknowns about gamma-ray bursts. Recent observations have shown that the photons emitted from gamma-ray bursts all oscillate in the same direction, but for some reason, the polarization direction changes over time.
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- Gamma-ray bursts also seem to focus their energy in a narrow beam, rather than emitting it equally in every direction, meaning that our satellites are missing many of them. Astronomers estimate that, although satellites spot about one gamma-ray burst per day, roughly 500 are occurring within the same time period.
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-So far, gamma-ray bursts have only been detected in distant galaxies. However, it is possible for one to occur in our Milky Way galaxy. The Ordovician extinction, one of five big extinction events in our planet's history, happened around 450 million years ago and might have been caused by an ice age triggered by a gamma-ray burst.
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- If a new gamma-ray burst were to happen near Earth, it would strip our planet's protective ozone layer away and expose all life to deadly ultraviolet radiation.
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- Although scientists might appreciate the opportunity to witness a gamma-ray burst up close one day, they're also OK with not observing one in our home galaxy.
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- I’m ok with that. --------------- Other Reviews about Gamma Rays and Cosmic Rays:
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- 2986 - GAMMA RAYS - magnetars and neutron stars. If the neutron star is spinning very fast it can create a rotating magnetic field that is a ‘pulsar’ or a ‘magnetar” depending on how strong the magnetic field is. Our newest telescopes and instruments are beginning to measure the characteristics of these extreme stars.
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- 2956 - GAMMA RAY BURSTS - Long ago and far across the universe, an enormous burst of gamma rays unleashed more energy in a half-second than the sun will produce over its entire 10-billion-year lifetime. ½ second versus 10,000,000,000 years! The light got here on May 22, 2020, After examining the incredibly bright burst with optical, X-ray, near-infrared and radio wavelengths, astrophysists believe it potentially spotted the birth of a “magnetar“.
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- 2873 - GAMMA RAYS - are photons Cosmic “Rays” are particles. Gamma ray mystery covering years of research? Gamma Rays are essentially high energy light. They started out with the Big Bang and have been loosing energy as they travel though an expanding Universe. But, they also include processes created by cosmic ray interactions with interstellar gas, supernova explosions and interactions of energetic electrons with magnetic fields.
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- 2858 - COSMIC RAYS - where do they come from? Earth is being constantly bombarded from space by “cosmic rays” of an unknown origin! Mysterious cosmic rays traveling at speeds approaching that of light constantly pelt Earth’s upper atmosphere from the depths of space, creating high-energy collisions that dwarf those produced in even the most powerful particle colliders.
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- 2825 - GAMMA RAYS - mystery covering years of research? Gamma Rays are essentially high energy light. They started out with the Big Bang and have been loosing energy as they travel though an expanding Universe. But, they also include processes created by cosmic ray interactions with interstellar gas, supernova explosions and interactions of energetic electrons with magnetic fields.
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- 2821 - GAMMA RAY BURSTS - how often it happens? Would you like to see the most powerful explosion that occurs in the Universe? Don’t worry you do not have to stand too close. These explosions are at least 2,000,000,000 lightyears away. They occur once a day on average and one of these occurred in the constellation Hydra. Log on to http://grb.sonoma.edu/ and see the sky map with the Gamma Ray Bursts exploding in real time.
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- 2330 - Monday, December 27, 2004, the brightest flash of light in our history passed by Earth . It came from a neutron star, a remnant of a giant star that ended its live in a supernova explosion. These giant stars start out at 30 to 40 times the mass of our Sun.
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- June 6, 2021 GAMMA RAY BURSTS - caused by exploding stars? 3183
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--------------------- --- Monday, June 7, 2021 ---------------------------
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