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96-508: AstroSat is India's first dedicated multi-wavelength space telescope . It was launched on a PSLV-XL on 28 September 2015. With the success of this satellite, ISRO has proposed launching AstroSat-2 as a successor for AstroSat . After the success of the satellite-borne Indian X-ray Astronomy Experiment (IXAE), which was launched in 1996, the Indian Space Research Organization (ISRO) approved further development for

192-429: A bolometric flux comparable to a bright star of our galaxy despite a distance of billions of light years (compared to a few tens of light years for most visible stars). Most of this energy is released in gamma rays, although some GRBs have extremely luminous optical counterparts as well. GRB 080319B , for example, was accompanied by an optical counterpart that peaked at a visible magnitude of 5.8, comparable to that of

288-409: A supernova or superluminous supernova as a high-mass star implodes to form a neutron star or a black hole . From gravitational wave observations, §   short-duration (sGRB) events describe a subclass of GRB signals that are now known to originate from the cataclysmic merger of binary neutron stars. The sources of most GRB are billions of light years away from Earth , implying that

384-411: A "short" population with an average duration of about 0.3 seconds and a "long" population with an average duration of about 30 seconds. Both distributions are very broad with a significant overlap region in which the identity of a given event is not clear from duration alone. Additional classes beyond this two-tiered system have been proposed on both observational and theoretical grounds. Events with

480-452: A GRB, because the oceans were mostly oligotrophic and clear. The late Ordovician species of trilobites that spent portions of their lives in the plankton layer near the ocean surface were much harder hit than deep-water dwellers, which tended to remain within quite restricted areas. This is in contrast to the usual pattern of extinction events, wherein species with more widely spread populations typically fare better. A possible explanation

576-503: A carbon–oxygen core and a companion neutron star or a black hole. Furthermore, the energy of GRBs in the model is isotropic instead of collimated. The creators of the model have noted the numerous drawbacks of the standard "fireball" model as motivation for developing the model, such as the markedly different energetics for supernova and gamma-ray bursts, and the fact that the existence of extremely narrow beaming angles have never been observationally corroborated. The closest analogs within

672-482: A duration of less than about two seconds are classified as short gamma-ray bursts (sGRB). These account for about 30% of gamma-ray bursts, but until 2005, no afterglow had been successfully detected from any short event and little was known about their origins. Following this, several dozen short gamma-ray burst afterglows were detected and localized, several of them associated with regions of little or no star formation, such as large elliptical galaxies . This ruled out

768-432: A few cases particularly well-localized bursts (those whose positions were determined with what was then a high degree of accuracy) could be clearly shown to have no bright objects of any nature consistent with the position derived from the detecting satellites. This suggested an origin of either very faint stars or extremely distant galaxies. Even the most accurate positions contained numerous faint stars and galaxies, and it

864-523: A flurry of discoveries from the James Webb Space Telescope , GRB 090429B was the most distant known object in the universe. In October 2018, astronomers reported that GRB 150101B (detected in 2015) and GW170817 , a gravitational wave event detected in 2017 (which has been associated with GRB170817A, a burst detected 1.7 seconds later), may have been produced by the same mechanism – the merger of two neutron stars . The similarities between

960-617: A full-fledged astronomy satellite, AstroSat , in 2004. A number of astronomy research institutions in India, and abroad have jointly built instruments for the satellite. Important areas requiring coverage include studies of astrophysical objects ranging from nearby Solar System objects to distant stars and objects at cosmological distances; timing studies of variables ranging from pulsations of hot white dwarfs to those of active galactic nuclei can be conducted with AstroSat as well, with time scales ranging from milliseconds to days. AstroSat

1056-546: A galaxy located 9.3 billion light-years away from Earth. The galaxy called AUDFs01 was discovered by a team of Astronomers led by Kanak Saha from the Inter-University Centre for Astronomy and Astrophysics , Pune. In 2019 a documentary titled Indian Space Dreams on the developmental journey of Astrosat, and directed by Sue Sudbury, was released. Space telescope In 1946, American theoretical astrophysicist Lyman Spitzer , "father of Hubble" proposed to put

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1152-540: A gamma-ray burst in the Milky Way pointed directly at Earth would likely sterilize the planet or effect a mass extinction . The Late Ordovician mass extinction has been hypothesised by some researchers to have occurred as a result of such a gamma-ray burst. GRB signals were first detected in 1967 by the Vela satellites , which were designed to detect covert nuclear weapons tests ; after thorough declassification analysis, this

1248-420: A gamma-ray burst was one teraelectronvolt , from GRB 190114C in 2019. (Note, this is about a thousand times lower energy than the highest energy light observed from any source, which is 1.4 petaelectronvolts as of the year 2021. ) The light curves of gamma-ray bursts are extremely diverse and complex. No two gamma-ray burst light curves are identical, with large variation observed in almost every property:

1344-464: A kilonova associated with short GRB 130603B was reported in 2013. The mean duration of sGRB events of around 200 milliseconds implied (due to causality ) that the sources must be of very small physical diameter in stellar terms: less than 0.2 light-seconds (60,000 km or 37,000 miles) – about four times the Earth's diameter. The observation of minutes to hours of X-ray flashes after an sGRB

1440-425: A link to massive stars, confirming the short events to be physically distinct from long events. In addition, there had been no association with supernovae. The true nature of these objects was thus initially unknown, but the leading hypothesis was that they originated from the mergers of binary neutron stars or a neutron star with a black hole . Such mergers were hypothesized to produce kilonovae , and evidence for

1536-579: A neutron star. The last outburst was detected in 2019 after about 26 years. The accreting neutron star in this Be/X-ray binary system was found to be an ultraluminous X-ray Pulsar (ULXP) making it the second closest ULXP and the first ULXP in our neighbouring Galaxy in the Magellanic Clouds . This source is the first ULX pulsar discovered with the AstroSat mission and only the eight known ULX pulsar. In August 2020, AstroSat had detected extreme-UV light from

1632-524: A population they are likely less collimated than long GRBs or possibly not collimated at all in some cases. Because of the immense distances of most gamma-ray burst sources from Earth, identification of the progenitors, the systems that produce these explosions, is challenging. The association of some long GRBs with supernovae and the fact that their host galaxies are rapidly star-forming offer very strong evidence that long gamma-ray bursts are associated with massive stars. The most widely accepted mechanism for

1728-411: A possible global reduction of 25–35%, with as much as 75% in certain locations, an effect that would last for years. This reduction is enough to cause a dangerously elevated UV index at the surface. Secondly, the nitrogen oxides cause photochemical smog , which darkens the sky and blocks out parts of the sunlight spectrum. This would affect photosynthesis , but models show only about a 1% reduction of

1824-486: A result of low sensitivity of current detectors to long-duration events, rather than a reflection of their true frequency. A 2013 study, on the other hand, shows that the existing evidence for a separate ultra-long GRB population with a new type of progenitor is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion. Gamma-ray bursts are very bright as observed from Earth despite their typically immense distances. An average long GRB has

1920-573: A second to tens of seconds. This ultraviolet radiation could potentially reach dangerous levels depending on the exact nature and distance of the burst, but it seems unlikely to be able to cause a global catastrophe for life on Earth. The long-term effects from a nearby burst are more dangerous. Gamma rays cause chemical reactions in the atmosphere involving oxygen and nitrogen molecules , creating first nitrogen oxide then nitrogen dioxide gas. The nitrogen oxides cause dangerous effects on three levels. First, they deplete ozone , with models showing

2016-437: A special galaxy cluster that is more than 800 million light years away from Earth. Named abell 2256 the galaxy cluster is made of three separate cluster of galaxy that are all merging with one another to eventually form a single massive cluster in the future. The three massive cluster contain more than 500 galaxies and the cluster is almost 100 times larger and more than 1500 times massive as our own galaxy. On 26 September 2018,

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2112-535: A support cell for AstroSat at IUCAA , Pune . A MoU was signed between ISRO and IUCAA in May 2016. The support cell has been set up to give opportunity to the scientific community in making proposals on processing and usage of AstroSat data. The support cell will provide necessary resource materials, tools, training and help to the guest observers. The Astrosat project is a collaborative effort of many different research institutions. The participants are: A gamma-ray burst

2208-561: A telescope in space. Spitzer's proposal called for a large telescope that would not be hindered by Earth's atmosphere. After lobbying in the 1960s and 70s for such a system to be built, Spitzer's vision ultimately materialized into the Hubble Space Telescope , which was launched on April 24, 1990, by the Space Shuttle Discovery (STS-31). This was launched due to many efforts by Nancy Grace Roman, "mother of Hubble", who

2304-721: A very strong solar flare is another possibility. No gamma-ray bursts from within our own galaxy, the Milky Way , have been observed, and the question of whether one has ever occurred remains unresolved. In light of evolving understanding of gamma-ray bursts and their progenitors, the scientific literature records a growing number of local, past, and future GRB candidates. Long duration GRBs are related to superluminous supernovae, or hypernovae, and most luminous blue variables (LBVs) and rapidly spinning Wolf–Rayet stars are thought to end their life cycles in core-collapse supernovae with an associated long-duration GRB. Knowledge of GRBs, however,

2400-453: Is a 50% chance that such a lethal GRB took place within two kiloparsecs of Earth during the last 500 million years, causing one of the major mass extinction events. The major Ordovician–Silurian extinction event 450 million years ago may have been caused by a GRB. Estimates suggest that approximately 20–60% of the total phytoplankton biomass in the Ordovician oceans would have perished in

2496-420: Is a multi- wavelength astronomy mission on an IRS-class satellite into a near-Earth, equatorial orbit . The five instruments on board cover the visible (320–530 nm), near UV (180–300 nm), far UV (130–180 nm), soft X-ray (0.3–8 keV and 2–10 keV) and hard X-ray (3–80 keV and 10–150 keV) regions of the electromagnetic spectrum . The sanctioned cost of Astrosat was ₹177.85 crore. Astrosat

2592-638: Is a small X-ray telescope satellite for studying the explosions of massive stars by analysing the resulting gamma-ray bursts, developed by China National Space Administration (CNSA), Chinese Academy of Sciences (CAS) and the French Space Agency ( CNES ), launched on 22 June 2024 (07:00:00 UTC). The Taiwan Space Agency is launching a cubesat called The Gamma-ray Transients Monitor to track GRBs and other bright gamma-ray transients with energies ranging from 50 keV to 2 MeV in Q4 2026. New developments since

2688-532: Is difficult to observe a burst's position at longer wavelengths immediately after the initial burst. The breakthrough came in February 1997 when the satellite BeppoSAX detected a gamma-ray burst ( GRB 970228 ) and when the X-ray camera was pointed towards the direction from which the burst had originated, it detected fading X-ray emission. The William Herschel Telescope identified a fading optical counterpart 20 hours after

2784-461: Is estimated that just 1% of all TDEs are jetted events. The means by which gamma-ray bursts convert energy into radiation remains poorly understood, and as of 2010 there was still no generally accepted model for how this process occurs. Any successful model of GRB emission must explain the physical process for generating gamma-ray emission that matches the observed diversity of light curves, spectra, and other characteristics. Particularly challenging

2880-533: Is limited by the filtering and distortion of electromagnetic radiation ( scintillation or twinkling) due to the atmosphere . A telescope orbiting Earth outside the atmosphere is subject neither to twinkling nor to light pollution from artificial light sources on Earth. As a result, the angular resolution of space telescopes is often much higher than a ground-based telescope with a similar aperture . Many larger terrestrial telescopes, however, reduce atmospheric effects with adaptive optics . Space-based astronomy

2976-493: Is more important for frequency ranges that are outside the optical window and the radio window , the only two wavelength ranges of the electromagnetic spectrum that are not severely attenuated by the atmosphere. For example, X-ray astronomy is nearly impossible when done from Earth, and has reached its current importance in astronomy only due to orbiting X-ray telescopes such as the Chandra X-ray Observatory and

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3072-614: Is still operational. Swift is equipped with a very sensitive gamma-ray detector as well as on-board X-ray and optical telescopes, which can be rapidly and automatically slewed to observe afterglow emission following a burst. More recently, the Fermi mission was launched carrying the Gamma-Ray Burst Monitor , which detects bursts at a rate of several hundred per year, some of which are bright enough to be observed at extremely high energies with Fermi's Large Area Telescope . Meanwhile, on

3168-476: Is strong evidence that some short-duration gamma-ray bursts occur in systems with no star formation and no massive stars, such as elliptical galaxies and galaxy halos . The favored hypothesis for the origin of most short gamma-ray bursts is the merger of a binary system consisting of two neutron stars. According to this model, the two stars in a binary slowly spiral towards each other because gravitational radiation releases energy until tidal forces suddenly rip

3264-517: Is that in the course of a gravitational collapse and in reaching the event horizon of a black hole, all matter disintegrates into a burst of gamma radiation. This class of GRB-like events was first discovered through the detection of Swift J1644+57 (originally classified as GRB 110328A) by the Swift Gamma-Ray Burst Mission on 28 March 2011. This event had a gamma-ray duration of about 2 days, much longer than even ultra-long GRBs, and

3360-399: Is that trilobites remaining in deep water would be more shielded from the increased UV radiation associated with a GRB. Also supportive of this hypothesis is the fact that during the late Ordovician, burrowing bivalve species were less likely to go extinct than bivalves that lived on the surface. A case has been made that the 774–775 carbon-14 spike was the result of a short GRB, though

3456-420: Is the need to explain the very high efficiencies that are inferred from some explosions: some gamma-ray bursts may convert as much as half (or more) of the explosion energy into gamma-rays. Early observations of the bright optical counterparts to GRB 990123 and to GRB 080319B , whose optical light curves were extrapolations of the gamma-ray light spectra, have suggested that inverse Compton scattering may be

3552-467: Is toxic to a variety of organisms, including amphibian life, but models predict that it would not reach levels that would cause a serious global effect. The nitrates might in fact be of benefit to some plants. All in all, a GRB within a few kiloparsecs, with its energy directed towards Earth, will mostly damage life by raising the UV levels during the burst itself and for a few years thereafter. Models show that

3648-479: The Big Bang as the most energetic and luminous phenomenon ever known. Gamma-ray bursts can last from ten milliseconds to several hours. After the initial flash of gamma rays , a longer-lived § Afterglow is emitted, usually in the longer wavelengths of X-ray , ultraviolet , optical , infrared , microwave or radio frequencies. The intense radiation of most observed GRBs is thought to be released during

3744-487: The German Electron Synchrotron , stating that "Our measurements show that the energy released in very-high-energy gamma-rays is comparable to the amount radiated at all lower energies taken together". Short (time duration) GRBs appear to come from a lower-redshift (i.e. less distant) population and are less luminous than long GRBs. The degree of beaming in short bursts has not been accurately measured, but as

3840-633: The Nuclear Test Ban Treaty in 1963. On July 2, 1967, at 14:19 UTC , the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons signature. Uncertain what had happened but not considering the matter particularly urgent, the team at the Los Alamos National Laboratory , led by Ray Klebesadel , filed the data away for investigation. As additional Vela satellites were launched with better instruments,

3936-765: The Soviet space program (later succeeded by Roscosmos of Russia). As of 2022, many space observatories have already completed their missions, while others continue operating on extended time. However, the future availability of space telescopes and observatories depends on timely and sufficient funding. While future space observatories are planned by NASA, JAXA and the CNSA , scientists fear that there would be gaps in coverage that would not be covered immediately by future projects and this would affect research in fundamental science. On 16 January 2023, NASA announced preliminary considerations of several future space telescope programs, including

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4032-564: The XMM-Newton observatory . Infrared and ultraviolet are also largely blocked. Space telescopes are much more expensive to build than ground-based telescopes. Due to their location, space telescopes are also extremely difficult to maintain. The Hubble Space Telescope was serviced by the Space Shuttle , but most space telescopes cannot be serviced at all. Satellites have been launched and operated by NASA , ISRO , ESA , CNSA , JAXA and

4128-400: The 2000s include the recognition of short gamma-ray bursts as a separate class (likely from merging neutron stars and not associated with supernovae), the discovery of extended, erratic flaring activity at X-ray wavelengths lasting for many minutes after most GRBs, and the discovery of the most luminous ( GRB 080319B ) and the former most distant ( GRB 090423 ) objects in the universe. Prior to

4224-498: The Earth and never be detected. When a gamma-ray burst is pointed towards Earth, the focusing of its energy along a relatively narrow beam causes the burst to appear much brighter than it would have been were its energy emitted spherically. The total energy of typical gamma-ray bursts has been estimated at 3 × 10  J, – which is larger than the total energy (10  J) of ordinary supernovae (type Ia , Ibc , II ), with gamma-ray bursts also being more powerful than

4320-514: The GRB having originated in star-forming regions. In December 2022, astronomers reported the observation of GRB 211211A for 51 seconds, the first evidence of a long GRB produced by a neutron star merger . Following this, GRB 191019A (2019, 64s) and GRB 230307A (2023, 35s) have been argued to signify an emerging class of long GRBs which originate from neutron star mergers. ulGRB are defined as GRB lasting more than 10,000 seconds, covering

4416-520: The Great Observatory Technology Maturation Program, Habitable Worlds Observatory , and New Great Observatories. Gamma-ray burst In gamma-ray astronomy , gamma-ray bursts ( GRBs ) are immensely energetic events occurring in distant galaxies which represent the brightest and "most powerful class of explosions [ sic ] in the universe." These extreme electromagnetic events are second only to

4512-455: The Los Alamos team continued to find inexplicable gamma-ray bursts in their data. By analyzing the different arrival times of the bursts as detected by different satellites, the team was able to determine rough estimates for the sky positions of 16 bursts and definitively rule out a terrestrial or solar origin. Contrary to popular belief, the data was never classified. After thorough analysis,

4608-518: The Milky Way galaxy and have been harmless to Earth. However, if a GRB were to occur within the Milky Way within 5,000 to 8,000 light-years and its emission were beamed straight towards Earth, the effects could be harmful and potentially devastating for its ecosystems . Currently, orbiting satellites detect on average approximately one GRB per day. The closest observed GRB as of March 2014 was GRB 980425 , located 40 megaparsecs (130,000,000 ly) away ( z =0.0085) in an SBc-type dwarf galaxy. GRB 980425

4704-539: The Milky Way galaxy of the stars producing long gamma-ray bursts are likely the Wolf–Rayet stars , extremely hot and massive stars, which have shed most or all of their hydrogen envelope. Eta Carinae , Apep , and WR 104 have been cited as possible future gamma-ray burst progenitors. It is unclear if any star in the Milky Way has the appropriate characteristics to produce a gamma-ray burst. The massive-star model probably does not explain all types of gamma-ray burst. There

4800-596: The UV/optical waveband, whereas the mass of the donating star is brightest in the optical band. The observatory will also carry out: In particular, the mission will train its instruments at active galactic nuclei, which are believed to contain super-massive black holes. The scientific payload contains six instruments. The Ground Command and Control Center for Astrosat is the ISRO Telemetry, Tracking and Command Network (ISTRAC) at Bangalore, India. Command and control of

4896-418: The archival data of AstroSat was publicly released. As of 28 September 2018, data from AstroSat has been cited in around 100 publications in refereed journals. This figure is expected to rise after the public release of data from AstroSat. In 2019 AstroSat observed a very rare X-ray outburst in a Be/X-ray binary system RX J0209.6-7427. Only a couple of rare outbursts have been observed from this source hosting

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4992-444: The beam) can be estimated directly by observing the achromatic "jet breaks" in afterglow light curves: a time after which the slowly decaying afterglow begins to fade rapidly as the jet slows and can no longer beam its radiation as effectively. Observations suggest significant variation in the jet angle from between 2 and 20 degrees. Because their energy is strongly focused, the gamma rays emitted by most bursts are expected to miss

5088-553: The burst. Once the GRB faded, deep imaging was able to identify a faint, distant host galaxy at the location of the GRB as pinpointed by the optical afterglow. Because of the very faint luminosity of this galaxy, its exact distance was not measured for several years. Well after then, another major breakthrough occurred with the next event registered by BeppoSAX, GRB 970508 . This event was localized within four hours of its discovery, allowing research teams to begin making observations much sooner than any previous burst. The spectrum of

5184-464: The destructive effects of this increase can cause up to 16 times the normal levels of DNA damage. It has proved difficult to assess a reliable evaluation of the consequences of this on the terrestrial ecosystem, because of the uncertainty in biological field and laboratory data. There is a very good chance (but no certainty) that at least one lethal GRB took place during the past 5 billion years close enough to Earth as to significantly damage life. There

5280-409: The development of a number of additional instruments designed specifically to explore the nature of GRBs, especially in the earliest moments following the explosion. The first such mission, HETE-2 , was launched in 2000 and functioned until 2006, providing most of the major discoveries during this period. One of the most successful space missions to date, Swift , was launched in 2004 and as of May 2024

5376-586: The dimmest naked-eye stars despite the burst's distance of 7.5 billion light years. This combination of brightness and distance implies an extremely energetic source. Assuming the gamma-ray explosion to be spherical, the energy output of GRB 080319B would be within a factor of two of the rest-mass energy of the Sun (the energy which would be released were the Sun to be converted entirely into radiation). Gamma-ray bursts are thought to be highly focused explosions, with most of

5472-399: The discovery of GRBs, astronomers searched for a counterpart at other wavelengths: i.e., any astronomical object in positional coincidence with a recently observed burst. Astronomers considered many distinct classes of objects, including white dwarfs , pulsars , supernovae , globular clusters , quasars , Seyfert galaxies , and BL Lac objects . All such searches were unsuccessful, and in

5568-472: The distribution of GRBs is isotropic  – not biased towards any particular direction in space. If the sources were from within our own galaxy, they would be strongly concentrated in or near the galactic plane. The absence of any such pattern in the case of GRBs provided strong evidence that gamma-ray bursts must come from beyond the Milky Way. However, some Milky Way models are still consistent with an isotropic distribution. For decades after

5664-400: The dominant process in some events. In this model, pre-existing low-energy photons are scattered by relativistic electrons within the explosion, augmenting their energy by a large factor and transforming them into gamma-rays. The nature of the longer-wavelength afterglow emission (ranging from X-ray through radio ) that follows gamma-ray bursts is better understood. Any energy released by

5760-667: The duration of observable emission can vary from milliseconds to tens of minutes, there can be a single peak or several individual subpulses, and individual peaks can be symmetric or with fast brightening and very slow fading. Some bursts are preceded by a " precursor " event, a weak burst that is then followed (after seconds to minutes of no emission at all) by the much more intense "true" bursting episode. The light curves of some events have extremely chaotic and complicated profiles with almost no discernible patterns. Although some light curves can be roughly reproduced using certain simplified models, little progress has been made in understanding

5856-417: The explosion energy collimated into a narrow jet . The jets of gamma-ray bursts are ultrarelativistic , and are the most relativistic jets in the universe. The matter in gamma-ray burst jets may also become superluminal , or faster than the speed of light in the jet medium, with there also being effects of time reversibility . The approximate angular width of the jet (that is, the degree of spread of

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5952-412: The explosion not radiated away in the burst itself takes the form of matter or energy moving outward at nearly the speed of light. As this matter collides with the surrounding interstellar gas , it creates a relativistic shock wave that then propagates forward into interstellar space. A second shock wave, the reverse shock, may propagate back into the ejected matter. Extremely energetic electrons within

6048-446: The explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime) and extremely rare (a few per galaxy per million years). All GRBs in recorded history have originated from outside the Milky Way galaxy , although a related class of phenomena, soft gamma repeaters , are associated with magnetars within our galaxy. This may be self-evident, since

6144-401: The extreme isotropic energy totals as being true, with there being no need to correct for beaming. They also note that the extreme beaming angles in the standard "fireball" model have never been physically corroborated. With the discovery of GRB 190114C , astronomers may have been missing half of the total energy that gamma-ray bursts produce, with Konstancja Satalecka, an astrophysicist at

6240-554: The findings were published in 1973 as an Astrophysical Journal article entitled "Observations of Gamma-Ray Bursts of Cosmic Origin". Most early hypotheses of gamma-ray bursts posited nearby sources within the Milky Way Galaxy . From 1991, the Compton Gamma Ray Observatory (CGRO) and its Burst and Transient Source Explorer ( BATSE ) instrument, an extremely sensitive gamma-ray detector, provided data that showed

6336-431: The full diversity observed. Many classification schemes have been proposed, but these are often based solely on differences in the appearance of light curves and may not always reflect a true physical difference in the progenitors of the explosions. However, plots of the distribution of the observed duration for a large number of gamma-ray bursts show a clear bimodality , suggesting the existence of two separate populations:

6432-502: The galaxies and supernovae associated with the bursts—clarified the distance and luminosity of GRBs, definitively placing them in distant galaxies. Gamma-ray bursts were first observed in the late 1960s by the U.S. Vela satellites, which were built to detect gamma radiation pulses emitted by nuclear weapons tested in space. The United States suspected that the Soviet Union might attempt to conduct secret nuclear tests after signing

6528-468: The galaxy have been observed to affect the Earth's atmosphere. Earth's atmosphere is very effective at absorbing high energy electromagnetic radiation such as x-rays and gamma rays, so these types of radiation would not reach any dangerous levels at the surface during the burst event itself. The immediate effect on life on Earth from a GRB within a few kilo parsecs would only be a short increase in ultraviolet radiation at ground level, lasting from less than

6624-481: The ground, numerous optical telescopes have been built or modified to incorporate robotic control software that responds immediately to signals sent through the Gamma-ray Burst Coordinates Network . This allows the telescopes to rapidly repoint towards a GRB, often within seconds of receiving the signal and while the gamma-ray emission itself is still ongoing. The Space Variable Objects Monitor

6720-454: The high energy regions, i.e., UV, X-ray and visible wavelength, would be covered by the dedicated satellite-borne instrumentation of AstroSat . The mission would also study near simultaneous multi-wavelength data from different variable sources. In a binary system , for example, regions near the compact object emit predominantly in the X-ray , with the accretion disc emitting most of its light in

6816-472: The majority of the population and because they tend to have the brightest afterglows, they have been observed in much greater detail than their short counterparts. Almost every well-studied long gamma-ray burst has been linked to a galaxy with rapid star formation, and in many cases to a core-collapse supernova as well, unambiguously associating long GRBs with the deaths of massive stars. Long GRB afterglow observations, at high redshift, are also consistent with

6912-511: The neutron stars apart and they collapse into a single black hole. The infall of matter into the new black hole produces an accretion disk and releases a burst of energy, analogous to the collapsar model. Numerous other models have also been proposed to explain short gamma-ray bursts, including the merger of a neutron star and a black hole, the accretion-induced collapse of a neutron star, or the evaporation of primordial black holes . An alternative explanation proposed by Friedwardt Winterberg

7008-522: The object revealed a redshift of z  = 0.835, placing the burst at a distance of roughly 6 billion  light years from Earth. This was the first accurate determination of the distance to a GRB, and together with the discovery of the host galaxy of 970228 proved that GRBs occur in extremely distant galaxies. Within a few months, the controversy about the distance scale ended: GRBs were extragalactic events originating within faint galaxies at enormous distances. The following year, GRB 980425

7104-413: The origin of long-duration GRBs is the collapsar model, in which the core of an extremely massive, low- metallicity , rapidly rotating star collapses into a black hole in the final stages of its evolution . Matter near the star's core rains down towards the center and swirls into a high-density accretion disk . The infall of this material into a black hole drives a pair of relativistic jets out along

7200-431: The rare phenomenon of a 6 billion year old small star or blue straggler feeding off and sucking out the mass and energy of a bigger companion star. On 31 May 2017, Astrosat , Chandra X-ray Observatory and Hubble Space Telescope simultaneously detected a coronal explosion on the nearest planet-hosting star Proxima Centauri On 6 November 2017 Nature Astronomy published a paper from Indian astronomers measuring

7296-410: The rotational axis, which pummel through the stellar envelope and eventually break through the stellar surface and radiate as gamma rays. Some alternative models replace the black hole with a newly formed magnetar , although most other aspects of the model (the collapse of the core of a massive star and the formation of relativistic jets) are the same. However, a new model which has gained support and

7392-512: The shock wave are accelerated by strong local magnetic fields and radiate as synchrotron emission across most of the electromagnetic spectrum . This model has generally been successful in modeling the behavior of many observed afterglows at late times (generally, hours to days after the explosion), although there are difficulties explaining all features of the afterglow very shortly after the gamma-ray burst has occurred. Gamma ray bursts can have harmful or destructive effects on life. Considering

7488-702: The spacecraft, and scientific data downloads is possible during every visible pass over Bangalore. 10 out of 14 orbits per day are visible to the ground station. The satellite is capable of gathering 420 gigabits of data every day that can be downloaded during the 10 visible orbits by the Tracking and Data receiving center of ISRO in Bangalore. A third 11-meter antenna at the Indian Deep Space Network (IDSN) became operational in July 2009 to track Astrosat . ISRO has set up

7584-401: The total sunlight spectrum, lasting a few years. However, the smog could potentially cause a cooling effect on Earth's climate, producing a "cosmic winter" (similar to an impact winter , but without an impact), but only if it occurs simultaneously with a global climate instability. Thirdly, the elevated nitrogen dioxide levels in the atmosphere would wash out and produce acid rain . Nitric acid

7680-426: The two events, in terms of gamma ray , optical , and x-ray emissions, as well as to the nature of the associated host galaxies , were considered "striking", suggesting the two separate events may both be the result of the merger of neutron stars, and both may be a kilonova , which may be more common in the universe than previously understood, according to the researchers. The highest energy light observed from

7776-475: The typical supernova. Very bright supernovae have been observed to accompany several of the nearest GRBs. Further support for focusing of the output of GRBs comes from observations of strong asymmetries in the spectra of nearby type Ic supernovae and from radio observations taken long after bursts when their jets are no longer relativistic. However, a competing model, the binary-driven hypernova model, developed by Remo Ruffini and others at ICRANet , accepts

7872-506: The universe as a whole, the safest environments for life similar to that on Earth are the lowest density regions in the outskirts of large galaxies. Our knowledge of galaxy types and their distribution suggests that life as we know it can only exist in about 10% of all galaxies. Furthermore, galaxies with a redshift, z , higher than 0.5 are unsuitable for life as we know it, because of their higher rate of GRBs and their stellar compactness. All GRBs observed to date have occurred well outside

7968-473: The unknown degree of collimation, but are probably comparable. Since GRBs are thought to involve beamed emission along two jets in opposing directions, only planets in the path of these jets would be subjected to the high energy gamma radiation. A GRB would be able to vaporize anything in its beams out to around 200 light-years. Although nearby GRBs hitting Earth with a destructive shower of gamma rays are only hypothetical events, high energy processes across

8064-451: The upper range to the limit of the GRB duration distribution. They have been proposed to form a separate class, caused by the collapse of a blue supergiant star , a tidal disruption event or a new-born magnetar . Only a small number have been identified to date, their primary characteristic being their gamma ray emission duration. The most studied ultra-long events include GRB 101225A and GRB 111209A . The low detection rate may be

8160-693: The variations of X-ray polarisation of the Crab Pulsar in the Taurus constellation. This study was a project conducted by scientists from Tata Institute of Fundamental Research , Mumbai; the Vikram Sarabhai Space Centre , Thiruvananthapuram; ISRO Satellite Centre Bengaluru; the Inter-University Centre for Astronomy and Astrophysics , Pune; and the Physical Research Laboratory , Ahmedabad. In July 2018, Astrosat has captured an image of

8256-419: Was detected by Astrosat on 5 January 2017. There was a confusion whether this event was related to the gravitational wave signal detected by LIGO from the black hole merger event GW170104 on 4 January 2017. Astrosat helped in distinguishing between the two events. The gamma-ray burst from 4 January 2017 was identified as a distinct supernova explosion that would form a black hole. Astrosat also captured

8352-589: Was detected in many frequencies for months and years after. It occurred at the center of a small elliptical galaxy at redshift 3.8 billion light years away. This event has been accepted as a tidal disruption event (TDE), where a star wanders too close to a supermassive black hole , shredding the star. In the case of Swift J1644+57, an astrophysical jet traveling at near the speed of light was launched, and lasted roughly 1.5 years before turning off. Since 2011, only 4 jetted TDEs have been discovered, of which 3 were detected in gamma-rays (including Swift J1644+57). It

8448-454: Was developed by the Italian astrophysicist Remo Ruffini and other scientists at ICRANet is that of the binary-driven hypernova (BdHN) model. The model succeeds and improves upon both the fireshell model and the induced gravitational collapse (IGC) paradigm suggested before, and explains all aspects of gamma-ray bursts. The model posits long gamma-ray bursts as occurring in binary systems with

8544-572: Was far less energetic than the average GRB and was associated with the Type Ib supernova SN 1998bw . Estimating the exact rate at which GRBs occur is difficult; for a galaxy of approximately the same size as the Milky Way , estimates of the expected rate (for long-duration GRBs) can range from one burst every 10,000 years, to one burst every 1,000,000 years. Only a small percentage of these would be beamed towards Earth. Estimates of rate of occurrence of short-duration GRBs are even more uncertain because of

8640-492: Was finally conclusively established in 2017, when short GRB 170817A co-occurred with the detection of gravitational wave GW170817 , a signal from the merger of two neutron stars. Unrelated to these cataclysmic origins, short-duration gamma-ray signals are also produced by giant flares from soft gamma repeaters in nearby galaxies. Most observed events (70%) have a duration of greater than two seconds and are classified as long gamma-ray bursts. Because these events constitute

8736-408: Was followed within a day by a bright supernova ( SN 1998bw ), coincident in location, indicating a clear connection between GRBs and the deaths of very massive stars. This burst provided the first strong clue about the nature of the systems that produce GRBs. BeppoSAX functioned until 2002 and CGRO (with BATSE) was deorbited in 2000. However, the revolution in the study of gamma-ray bursts motivated

8832-485: Was published as academic research in 1973. Following their discovery, hundreds of theoretical models were proposed to explain these bursts, such as collisions between comets and neutron stars . Little information was available to verify these models until the 1997 detection of the first X-ray and optical afterglows and direct measurement of their redshifts using optical spectroscopy , and thus their distances and energy outputs. These discoveries—and subsequent studies of

8928-424: Was seen as consistent with small particles of a precursor object like a neutron star initially being swallowed by a black hole in less than two seconds, followed by some hours of lower-energy events as remaining fragments of tidally disrupted neutron star material (no longer neutronium ) would remain in orbit, spiraling into the black hole over a longer period of time. The origin of short gamma-ray bursts in kilonovae

9024-597: Was successfully launched on 28 September 2015 from the Satish Dhawan Space Centre on board a PSLV-XL vehicle at 10:00AM. AstroSat is a proposal-driven general purpose observatory, with main scientific focus on: AstroSat performs multi-wavelength observations covering spectral bands from radio, optical, IR, UV, and X-ray wavelengths. Both individual studies of specific sources of interest and surveys are undertaken. While radio, optical, and IR observations would be coordinated through ground-based telescopes,

9120-608: Was the first Chief of Astronomy and first female executive at NASA. She was a program scientist that worked to convince NASA, Congress, and others that Hubble was "very well worth doing". The first operational space telescopes were the American Orbiting Astronomical Observatory , OAO-2 launched in 1968, and the Soviet Orion 1 ultraviolet telescope aboard space station Salyut 1 in 1971. Performing astronomy from ground-based observatories on Earth

9216-466: Was widely agreed that final resolution of the origins of cosmic gamma-ray bursts would require both new satellites and faster communication. Several models for the origin of gamma-ray bursts postulated that the initial burst of gamma rays should be followed by afterglow : slowly fading emission at longer wavelengths created by collisions between the burst ejecta and interstellar gas. Early searches for this afterglow were unsuccessful, largely because it

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