Swift Gamma-Ray Burst Mission
Encyclopedia
The Swift Gamma-Ray Burst Mission consists of a robotic spacecraft
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 called Swift, which was launched into orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

 on 20 November 2004, 17:16:00 UTC on a Delta II
Delta II
Delta II was an American space launch system, originally designed and built by McDonnell Douglas. Delta II is part of the Delta rocket family and was in service from 1989 until November 1, 2011...

 7320-10C expendable launch vehicle. Swift is managed by the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...

, and was developed by an international consortium from the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, and Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. It is part of NASA's Medium Explorer Program (MIDEX).

Overview

Swift is a multi-wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

  space-based observatory
Space observatory
A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects...

 dedicated to the study of gamma-ray bursts (GRBs). Its three instruments work together to observe GRBs and their afterglows in the gamma-ray, X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

, ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

, and optical wavebands.

Based on continuous scans of the area of the sky which one of the instruments monitors, Swift uses momentum wheel
Momentum wheel
A reaction wheel is a type of flywheel used primarily by spacecraft for attitude control without using fuel for rockets or other reaction devices....

s to autonomously slew into the direction of possible GRBs. The name "Swift" is not a mission-related acronym, but rather a reference to the instrument's rapid slew capability, and the nimble bird of the same name
Swift
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...

. All of Swifts discoveries are transmitted to the ground and those data are available to other observatories which join Swift in observing the GRBs.

In the time between GRB events, Swift is available for other scientific investigations, and scientists from universities and other organisations can submit proposals for observations.

The Swift Mission Operation Center (MOC), where commanding of the satellite is performed, is located in State College, Pennsylvania
State College, Pennsylvania
State College is the largest borough in Centre County in the U.S. state of Pennsylvania. It is the principal city of the State College, Pennsylvania Metropolitan Statistical Area which encompasses all of Centre County. As of the 2010 census, the borough population was 42,034, and roughly double...

 and operated by the Pennsylvania State University
Pennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...

 and industry subcontractors. The Swift main ground station is located at the Broglio Space Centre near Malindi
Malindi
Malindi is a town on Malindi Bay at the mouth of the Galana River, lying on the Indian Ocean coast of Kenya. It is 120 kilometres northeast of Mombasa. The population of Malindi is 117,735 . It is the capital of the Malindi District.Tourism is the major industry in Malindi. The city is...

 on the coast of Eastern Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

, and is operated by the Italian Space Agency
Italian Space Agency
The Italian Space Agency is a government agency established in 1988 to fund, regulate and coordinate space exploration activities in Italy...

. The Swift Science Data Center (SDC) and archive are located at the Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...

 outside Washington D.C. The UK Swift Science Data Centre is located at the University of Leicester
University of Leicester
The University of Leicester is a research-led university based in Leicester, England. The main campus is a mile south of the city centre, adjacent to Victoria Park and Wyggeston and Queen Elizabeth I College....

.

The Swift spacecraft bus was built by Spectrum Astro, which was later acquired by General Dynamics Advanced Information Systems
General Dynamics
General Dynamics Corporation is a U.S. defense conglomerate formed by mergers and divestitures, and as of 2008 it is the fifth largest defense contractor in the world. Its headquarters are in West Falls Church , unincorporated Fairfax County, Virginia, in the Falls Church area.The company has...

.

Burst Alert Telescope (BAT)

The BAT detects GRBs events and computes its coordinates in the sky. It covers a large fraction of the sky (over one steradian
Steradian
The steradian is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a plane...

 fully coded, three steradians partially coded; by comparison, the full sky solid angle is 4π or about 12.6 steradians). It locates the position of each event with an accuracy of 1 to 4 arc-minutes within 15 second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

s. This crude position is immediately relayed to the ground, and some wide-field, rapid-slew ground-based telescopes can catch the GRB with this information. The BAT uses a coded-aperture mask
Coded aperture
Coded Apertures or Coded-Aperture Masks are grids, gratings, or other patterns of materials opaque to various wavelengths of light. The wavelengths are usually high-energy radiation such as X-rays and gamma rays. By blocking and unblocking light in a known pattern, a coded "shadow" is cast upon a...

 of 52,000 randomly placed 5 mm lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 tiles, 1 metre above a detector plane of 32,768 four mm CdZnTe
Cadmium zinc telluride
Cadmium zinc telluride, or CZT, is a compound of cadmium, zinc and tellurium or, more strictly speaking, an alloy of cadmium telluride and zinc telluride. A direct bandgap semiconductor, it is used in a variety of applications, including radiation detectors, photorefractive gratings,...

 hard X-ray detector tiles; it is purpose-built for Swift. Energy range: 15–150 keV
Kev
Kev can refer to:*Kev Hawkins, a fictional character.*Kevin, a given name occasionally shortened to "Kev".*Kiloelectronvolt, a unit of energy who symbol is "KeV".* Krefelder Eislauf-VereinKEV can refer to:...

.

X-ray Telescope (XRT)

The XRT can take images and perform spectral analysis
Spectral analysis
Spectral analysis or Spectrum analysis may refer to:* Spectrum analysis in chemistry and physics, a method of analyzing the chemical properties of matter from bands in their visible spectrum...

 of the GRB afterglow. This provides more precise location of the GRB, with a typical error circle of approximately 2 arcseconds radius. The XRT is also used to perform long-term monitoring of GRB afterglow light-curves for days to weeks after the event, depending on the brightness of the afterglow. The XRT uses a Wolter Type I X-ray telescope
Wolter telescope
A Wolter telescope is a telescope for X-rays using only grazing incidence optics. Visible light telescopes are built with lenses or parabolic mirrors at nearly normal incidence. Neither works well for X-rays. Lenses for visible light are made of a transparent material with an index of refraction...

 with 12 nested mirrors, focused onto a single MOS charge-coupled device
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...

 (CCD) similar to those used by the XMM-Newton
XMM-Newton
The XMM-Newton is an orbiting X-ray observatory launched by ESA in December 1999 on a Ariane 5 rocket...

 EPIC MOS cameras. On-board software allows fully automated observations, with the instrument selecting an appropriate observing mode for each object, based on its measured count rate. The telescope has an energy range of 0.2 - 10 keV
Kev
Kev can refer to:*Kev Hawkins, a fictional character.*Kevin, a given name occasionally shortened to "Kev".*Kiloelectronvolt, a unit of energy who symbol is "KeV".* Krefelder Eislauf-VereinKEV can refer to:...

.

Ultraviolet/Optical Telescope (UVOT)

After Swift has slewed towards a GRB, the UVOT is used to detect an optical afterglow. The UVOT provides a sub-arcsecond position and provides optical and ultra-violet photometry through lenticular filters and low -esolution spectra (170–650 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...

) through the use of its optical and UV grism
Grism
A grism is a combination of a prism and grating arranged so that light at a chosen central wavelength passes straight through. The advantage of this arrangement is that one and the same camera can be used both for imaging and spectroscopy without having to be moved...

s. The UVOT is also used to provide long-term follow-ups of GRB afterglow lightcurves. The UVOT is based on the XMM-Newton
XMM-Newton
The XMM-Newton is an orbiting X-ray observatory launched by ESA in December 1999 on a Ariane 5 rocket...

 mission's Optical Monitor (OM) instrument, with improved optics and upgraded onboard processing computers.

On November 9, 2011, UVOT photographed the asteroid 2005 YU55
2005 YU55
', also written as 2005 YU55, is a potentially hazardous asteroid 310 meters or about 400 m in diameter. It was discovered on 28 December 2005 by Robert S. McMillan at Steward Observatory, Kitt Peak. On 8 November 2011 it passed 0.85 lunar distances from the Earth...

 as the asteroid made a close flyby of the Earth.

Mission goals

The Swift mission has four key scientific objectives:
  • To determine the origin of GRBs. There seem to be at least two types of GRBs, only one of which can be explained with a hypernova
    Hypernova
    Hypernova , also known as a type 1c Supernova, refers to an incredibly large star that collapses at the end of its lifespan...

    , creating a gamma-ray beam. More data is needed to explore other explanations.
  • To use GRBs to expand understanding of the young universe
    Universe
    The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

    . GRBs seem to take place at "cosmological distances" of many millions or billions of light-years, which means they can be used to probe the distant, and therefore young, cosmos.
  • To conduct an all-sky survey which will be more sensitive than any previous one, and will add significantly to scientific knowledge of astronomical X-ray sources. Thus, it could also yield unexpected results.
  • To serve as a general purpose gamma-ray/X-ray/optical observatory platform, performing rapid "target of opportunity" observations of many transient astrophysical phenomena, such as supernova
    Supernova
    A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

    e.

Mission history

Swift was launched on November 20, 2004, and reached a near-perfect orbit of 586x601 km altitude, with an inclination of 20°.

On December 4, an anomaly occurred during instrument activation when the Thermo-Electric Cooler (TEC) Power Supply for the X-Ray Telescope did not turn on as expected. The XRT Team at Leicester
University of Leicester
The University of Leicester is a research-led university based in Leicester, England. The main campus is a mile south of the city centre, adjacent to Victoria Park and Wyggeston and Queen Elizabeth I College....

 and Penn State University were able to determine on December 8 that the XRT would be usable even without the TEC being operational. Additional testing on December 16 did not yield any further information as to the cause of the anomaly.

On December 17 at 07:28:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board an apparent gamma-ray burst during launch and early operations. The spacecraft did not autonomously slew to the burst since normal operation had not yet begun, and autonomous slewing was not yet enabled. Swift had its first GRB trigger during a period when the autonomous slewing was enabled on January 17, 2005, at about 12:55 UTC. It pointed the XRT telescope to the on-board computed coordinates and observed a bright X-ray source in the field of view.

On February 1, 2005,the mission team released the first light picture of the UVOT instrument and declared Swift operational.

As of May 2010, Swift has detected more than 500 GRBs, X-ray afterglows for more than 90% of them, and optical afterglows for more than 50% of them.

Notable detections

  • May 9, 2005: Swift detected GRB 050509B
    GRB 050509b
    GRB 050509B was a gamma ray burst observed by the NASA Swift satellite on May 9, 2005. It was the first short duration GRB for which an accurate positional measurement was made, accurate enough to locate it near to an elliptical galaxy lying at a redshift of 0.225.The significance of this finding...

    , a burst of gamma rays that lasted one-twentieth of a second. The detection marked the first time that the accurate location of a short-duration gamma-ray burst had been identified and the first detection of X-ray afterglow in an individual short burst.

  • September 4, 2005: Swift detected GRB 050904
    GRB 050904
    GRB 050904 is one of the most distant events ever observed.This gamma ray burst occurred in the constellation Pisces.The bright γ-ray flash, lasting about 200 seconds, was detected on September 4, 2005 by the Swift Gamma-Ray Burst Mission....

     with a redshift
    Redshift
    In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...

     value of 6.29 and a duration of 200 seconds (most of the detected bursts last about 10 seconds). It was also found to be the most distant yet detected, at approximately 12.6 billion light-year
    Light-year
    A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

    s.

  • February 18, 2006: Swift detected GRB 060218
    GRB 060218
    GRB 060218 was a gamma-ray burst with unusual characteristics never seen before. This GRB was detected by the Swift satellite on February 18, 2006, and its name is derived from the date...

    , an unusually long (about 2000 seconds) and nearby (about 440 million light-year
    Light-year
    A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

    s) burst, which was unusually dim despite its close distance, and may be an indication of an imminent supernova
    Supernova
    A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

    .

  • June 14, 2006: Swift detected GRB 060614
    GRB 060614
    GRB 060614 was a remarkable gamma-ray burst detected by the Swift satellite on June 14, 2006 with puzzling properties, which challenge current progenitor models....

    , a burst of gamma rays that lasted 102 seconds in a distant galaxy (about 1,6 Billion light years). No supernova was seen following this event (and GRB 060505 to deep limits) leading some to speculate that it represented a new class of progenitors. Others suggested that these events could have been massive star deaths, but ones which produced too little radioactive 56Ni to power a supernova explosion.

  • January 9, 2008: Swift was observing a supernova in NGC 2770
    NGC 2770
    NGC 2770 is a type SASc spiral galaxy located about 88 million light years away, in the constellation Lynx.It has been referred to as the 'Supernova Factory' as three supernovas have occurred there recently: SN 1999eh, SN 2007uy, and SN 2008D...

     when it witnessed an X-ray burst coming from the same galaxy. The source of this burst was found to be the beginning of another supernova, later called SN 2008D
    SN 2008D
    SN 2008D is a supernova detected with NASA's Swift X-ray telescope. The explosion of the supernova precursor star, in the spiral galaxy NGC 2770 SN 2008D is a supernova detected with NASA's Swift X-ray telescope. The explosion of the supernova precursor star, in the spiral galaxy NGC 2770 SN 2008D...

    . Never before had a supernova been seen at such an early stage in its evolution. Following this stroke of luck (position, time, most appropriate instruments), astronomers were able to study in detail this Type Ibc supernova
    Type Ib and Ic supernovae
    Types Ib and Ic supernovae are categories of stellar explosions that are caused by the core collapse of massive stars. These stars have shed their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon...

     with the Hubble Space Telescope
    Hubble Space Telescope
    The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

    , the Chandra X-ray Observatory
    Chandra X-ray Observatory
    The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit.Chandra...

    , the Very Large Array
    Very Large Array
    The Very Large Array is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles west of Socorro, New Mexico, USA...

     in New Mexico, the Gemini North telescope in Hawaii, Gemini South in Chile, the Keck I telescope in Hawaii, the 1.3m PAIRITEL telescope at Mt Hopkins, the 200-inch
    Hale telescope
    The Hale Telescope is a , 3.3 reflecting telescope at the Palomar Observatory in California, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation, he orchestrated the planning, design, and construction of the observatory, but did not live to see its commissioning...

     and 60-inch telescopes at the Palomar Observatory
    Palomar Observatory
    Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...

     in California, and the 3.5-meter telescope at the Apache Point Observatory
    Apache Point Observatory
    The Apache Point Observatory is located in the Sacramento Mountains in Sunspot, New Mexico 18 miles south of Cloudcroft. The observatory consists of the Astrophysical Research Consortium's 3.5-meter telescope, the Sloan Digital Sky Survey 2.5-m telescope with a 20" photometric telescope,...

     in New Mexico. The significance of this supernova was likened by discovery team leader Dr. Alicia Soderberg to that of the Rosetta Stone
    Rosetta Stone
    The Rosetta Stone is an ancient Egyptian granodiorite stele inscribed with a decree issued at Memphis in 196 BC on behalf of King Ptolemy V. The decree appears in three scripts: the upper text is Ancient Egyptian hieroglyphs, the middle portion Demotic script, and the lowest Ancient Greek...

     for egyptology.

  • February 8 and February 13, 2008: Swift provided critical information about the nature of Hanny's Voorwerp
    Hanny's Voorwerp
    ' , Dutch for Hanny's object, is an astronomical object of unknown nature. It was discovered in 2007 by Dutch school teacher Hanny van Arkel, while she was participating as an amateur volunteer in the Galaxy Zoo project...

    , mainly the absence of an ionizing source within the Voorwerp or in the neighboring IC 2497
    IC 2497
    IC 2497 is a spiral galaxy close to the intergalactic cloud Hanny's Voorwerp.IC 2497 is a former quasar, whose light lit up Hanny's Voorwerp, which is now a light echo of that extinct quasar. It is about away from Hanny's Voorwerp. The quasar shut down sometime in the last 70,000 years...

    .

  • March 19, 2008: Swift detected GRB 080319B
    GRB 080319B
    GRB 080319B was a remarkable gamma-ray burst detected by the Swift satellite at 06:12 UTC on March 19, 2008. The burst set a new record for the farthest object that could be seen with the naked eye; it had a peak apparent magnitude of 5.8 and remained visible to human eyes for approximately 30...

    , a burst of gamma rays amongst the brightest celestial objects ever witnessed. At 7.5 billion light-year
    Light-year
    A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

    s, Swift established a new record for the farthest object (briefly) visible to the naked eye. It was also said to be 2.5 million times intrinsically brighter than the previous brightest accepted supernova (SN 2005ap)
    SN 2005ap
    SN 2005ap was an extremely energetic type II supernova. It is reported to be the brightest supernova yet recorded, twice as bright as the previous record holder, SN 2006gy...

    . Swift observed a record four GRBs that day, which also coincided with the death of noted science-fiction writer Arthur C. Clarke
    Arthur C. Clarke
    Sir Arthur Charles Clarke, CBE, FRAS was a British science fiction author, inventor, and futurist, famous for his short stories and novels, among them 2001: A Space Odyssey, and as a host and commentator in the British television series Mysterious World. For many years, Robert A. Heinlein,...

    .

  • September 13, 2008: Swift detected GRB 080913
    GRB 080913
    GRB 080913 was a gamma-ray burst observed on September 13, 2008. The Swift Gamma-Ray Burst satellite made the detection, with follow-up and additional observations from ground-based observatories and instruments, including the Gamma-Ray Burst Optical/Near-Infrared Detector and the Very Large...

    , at the time the most distant GRB observed (12.8 billion light-years) until the observation of GRB 090423
    GRB 090423
    GRB 090423 is a gamma-ray burst detected by the Swift Gamma-Ray Burst Mission on April 23, 2009 at 07:55:19 UTC. The afterglow of GRB 090423 was detected in the infrared, and allowed astronomers to determine that the redshift of GRB 090423 is z = 8.2, which makes GRB 090423 the second...

     a few months later.

  • April 23, 2009: Swift detected GRB 090423
    GRB 090423
    GRB 090423 is a gamma-ray burst detected by the Swift Gamma-Ray Burst Mission on April 23, 2009 at 07:55:19 UTC. The afterglow of GRB 090423 was detected in the infrared, and allowed astronomers to determine that the redshift of GRB 090423 is z = 8.2, which makes GRB 090423 the second...

    , the most distant cosmic explosion ever seen at that time, at 13.035 billion light-years. In other words, the universe was only 630 million years old when this burst occurred.

  • April 29, 2009: Swift detected GRB 090429B
    GRB 090429B
    GRB 090429B was a gamma-ray burst first detected on 29 April 2009, the second detected that day. Though this burst was detected in 2009, it was not until 2011 that its distance was announced, have a redshift of z=9.4, becoming the most distant GRB known in May 2011, usurping GRB 090423.On 2009...

    , which was found by later analysis published in 2011 to be 13.14 billion light-years distant (approximately equivalent to 520 million years after the Big Bang), even farther than GRB 090423.

  • March 16, 2010, Swift tied its record by again detecting and localizing four bursts in a single day.

  • April 13, 2010: Swift detected its 500th GRB.

  • March 28, 2011: Swift detected GRB 110328A
    GRB 110328A
    GRB 110328A is the longest lasting gamma-ray burst detected by the Swift Gamma-Ray Burst Mission on March 28, 2011. The explosion occurred in the center of small galaxy in the Draco constellation, about 3.8 billion years ago....

    , which subsequent analysis showed to possibly be the signature of a star being disrupted by a black hole or the ignition of an active galactic nucleus."This is truly different from any explosive event we have seen before," said Joshua Bloom
    Joshua Bloom
    Joshua Simon Bloom is an American astrophysicist and associate professor of astronomy at the University of California, Berkeley. He received a Bachelor of Arts in astronomy and astrophysics and physics from the Harvard College in 1996, an M.Phil from Cambridge University in 1997, and a Ph.D...

     of the University of California
    University of California
    The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...

     at Berkeley
    Berkeley, California
    Berkeley is a city on the east shore of the San Francisco Bay in Northern California, United States. Its neighbors to the south are the cities of Oakland and Emeryville. To the north is the city of Albany and the unincorporated community of Kensington...

    , the lead author of the study published in the June issue of Science
    Science (journal)
    Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....

    .

External links

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