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Topic: Gamma ray bursters

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	Learn more about Gamma ray in the online encyclopedia. (Site not responding. Last check: 2007-11-07)
		Gamma rays (often denoted by the Greek letter gamma, γ) are an energetic form of electromagnetic radiation (see Electromagnetic spectrum) produced by radioactivity or other nuclear or subatomic processes such as electron-position annihilation.
		Gamma rays from nuclear fallout would probably cause the largest number of casualties in the event of the use of nuclear weapons in a nuclear war.
		Gamma rays, x-rays, visible light, and UV rays are all forms of electromagnetic radiation.
	www.onlineencyclopedia.org /g/ga/gamma_ray.html (841 words)

	Gamma ray burst - Wikipedia, the free encyclopedia
		Optical afterglow of gamma ray burst GRB-990123 (the bright dot within the white square and in the enlarged cutout) on 23 January 1999.
		GRB 971214, in 1998, was found to be the brightest observed GRB in the universe.
		A Soft gamma repeater is a type of magnetar which emits large bursts of gamma rays and X-rays at irregular intervals.
	en.wikipedia.org /wiki/Gamma_ray_burster (3483 words)

	Kids.net.au - Encyclopedia Gamma ray burster -
		The high proper motion reported for GRB 970228 was clearly erroneous, and in fact observations made by the Hubble Space Telescope in September 1997 showed no proper motion in the faint afterglow that remained from GRB 970228.
		The Hubble observations that showed GRB 990123 to be associated with a young galaxy tended to discourage theorists who believed that the bursts were due to collisions between neutron stars or the like, since that implied a fairly high density of dead stars and that was inconsistent with a young galaxy.
		The brightness of GRBs varies rapidly, implying that their source objects are quite small: whatever causes the brightness variation cannot travel faster than the speed of light across the object.
	www.kids.net.au /encyclopedia-wiki/ga/Gamma_ray_burst (3115 words)

	Gamma ray (Site not responding. Last check: 2007-11-07)
		Gamma rays (often denoted by the Greek letter gamma, γ) are an energetic form of electromagnetic radiation (see Electromagnetic spectrum) produced by radioactivity or other nuclear or subatomic processes such as electron-positron annihilation.
		Gamma rays are a form of ionizing radiation; they are more penetrating than either alpha or beta radiation, but less ionizing.
		In spite of their cancer-causing properties, gamma rays are also used to treat some types of cancer.
	www.sciencedaily.com /encyclopedia/gamma_ray (816 words)

	speculative fact, gamma ray bursters (Site not responding. Last check: 2007-11-07)
		Gamma rays are the most energetic form of light, with shorter wavelengths than ultraviolet and x-rays, and with energies between 100 kiloelectron Volts (keV), or 105 eV, up to 1015 eV.
		Gamma rays are produced in nuclear reactions, including fission in nuclear power plants or radioactive decay, fusion in nuclear bombs or stellar interiors, reactions in cyclotrons where the particles are speeded and constrained by magnetic fields, and more exotic events such as matter- antimatter annihilation.
		Gamma ray burster data require a compact source, and they suggest a close source, whose emissions are limited to the highest energies of light, and which has some kind of magnetic containment.
	www.sff.net /people/mmolvray/grb/grblog2.htm (4480 words)

	Gamma_ray_burst (Site not responding. Last check: 2007-11-07)
		In astronomy, gamma-ray bursts (GRBs) are the most luminous physical phenomenon known in the universe and are flashes of gamma rays that last from seconds to hours, the longer ones being followed by several days of X-ray afterglow.
		The "Swift Gamma Ray Burst Explorer" satellite, constructed by Spectrum Astro, was launched in November 2004 from Cape Canaveral, and became fully operational in April 2005.
		A Soft gamma repeater is an astronomical object, that is known to be a type of magnetar, which emits large bursts of gamma rays and X-rays at irregular intervals.
	www.comicscomics.com /search.php?title=Gamma_ray_burst (3673 words)

	In Search of Gamma-Ray Bursters (Site not responding. Last check: 2007-11-07)
		GRBs appear to be distributed isotropically in the sky, and there is a relative paucity of fainter bursts compared to brighter ones.
		This suggests that we are at the center of a spherically symmetric and bounded population of bursters.
		Deep near-infrared images of the six GRB error boxes which both meet the target criteria for this program and are reachable from northern latitudes have been obtained.
	www.astro.ucla.edu /~irlab/gallery/grb.htm (677 words)

	GRB - Gamma Ray Bursts
		The GRB is produced as the jetted cannonballs exit the supernova shell reheated by the collision, re-emitting their own radiation and boosting the light of the shell.
		The cosmological distance of such GRBs depends on the validity of the identification of the GRB with the source or galaxy that is measured, usually by redshift, to be distant.
		Gamma ray production by sonoluminescence in the water formed from cometary ice in colliding comets may be feasible.
	www.valdostamuseum.org /hamsmith/GRB.html (5661 words)

	Big Bertha Thing Gamma Ray Bursters
		While the satellite's gamma ray detector has poor resolution, a gamma-ray burst will generally have an X-ray component, which should allow the X-ray cameras to quickly pinpoint the source for observation by optical and other telescopes.
		At least one of the correlated optical sources may have had nothing to do with a gamma ray burst, and simply happened to be in the right place at the right time.
		There was a peak of gamma and X-ray emission 25 seconds after the event was first detected, followed by a somewhat smaller peak 40 seconds after the beginning of the event.
	www.geocities.com /tonylance/gammaray.html (2263 words)

	Gamma Ray Bursts
		When gamma rays are detected from an object, we can be sure that something very exciting is going on there.
		But many think the the gamma ray bursters are very far away from us and that they may be in very young galaxies.
		The gamma rays must have come from a very powerful event, like two neutron stars crashing together, because they have travelled across so much space and time to reach us.
	www.windows.ucar.edu /tour/link=/the_universe/GRB.html (217 words)

	Great Moments in Science, Ep 32, 1997
		The trouble with all our current gamma ray detectors is that they are not very precise in telling you where an object is. But this burster also emitted X-rays, and Beppo-SAX had a high-precision X-ray telescope on board, which gave a very accurate location for the gamma ray burster.
		Because the astronomers had observed this object with gamma rays, X-rays, radio waves and visible light, they had enough information to work out that this object was over 10 billion light years away - pretty darn close to the edge of the universe.
		Our gamma ray observatories can detect activity in about 10 billion galaxies, which means that the observatories should see about 1,000 gamma ray bursters each year, which is (in astronomical terms) fairly close to what they actually do see.
	www.abc.net.au /science/k2/moments/gmis9732.htm (727 words)

	The Cosmic Gamma Ray Burst Web Page (Site not responding. Last check: 2007-11-07)
		A study of gamma ray burst spectra shows one more thing that these mysterious, cosmological gamma ray bursts are not.
		Gamma ray bursts were discovered by accident in the 1960's, and for the past 30 years they've been the target of intense research and speculation by astronomers.
		BATSE was designed specifically for the study of the enigmatic gamma ray bursters and has led to a new understanding of their origin and distribution in the universe.
	www.batse.com (488 words)

	NOVA Online \| Death Star \| A Bad Day in the Milky Way
		But even BATSE could only watch the gamma-ray emissions from the bursters fade away, never to be seen again and leaving no clearly identifiable trace of their sources.
		The concerns arose after it was realized that a startling but natural explanation of the bursters' random positions and observed brightness was that they were located in distant galaxies, themselves randomly distributed in our sky.
		Regardless of the mechanism producing the burst, the intense flux of gamma rays would likely be stopped in the lower stratosphere by collisions with atmospheric nitrogen molecules.
	www.pbs.org /wgbh/nova/gamma/milkyway.html (855 words)

	[9.0] Mysteries Of The Universe (Site not responding. Last check: 2007-11-07)
		This theory suggests that cosmic rays caused by Type II supernovas, the result of the collapse of a massive star, will include the nuclei of heavy elements, which will not be found in the cosmic rays generated by Type I supernovas, caused by the detonation of a white dwarf.
		Although there is no way to determine the source of a cosmic ray from its direction of arrival, highly energetic events also produce high energy gamma rays, which generate air showers like those produced by cosmic rays.
		These high-energy gamma rays are not affected by galactic magnetic fields and so point straight back to their source.
	www.vectorsite.net /tastga9.html (4889 words)

	HOW FAR AWAY ARE GAMMA-RAY BURSTERS? (Site not responding. Last check: 2007-11-07)
		The positions of over 1000 gamma-ray bursts detected with the BATSE experiment on board of the Compton Gamma Ray Observatory are uniformly and randomly distributed in the sky, with no significant concentration to the galactic plane or to the galactic center.
		If the bursters are indeed at cosmological distances then a simple prediction follows: the weakest bursts should be redshifted, i.e.
		If the bursters are indeed at cosmological distances then they are the most luminous sources of electromagnetic radiation known in the universe.
	antwrp.gsfc.nasa.gov /diamond_jubilee/papers/pac/debate.html (329 words)

	Gamma Ray Bursts
		Cosmic Rays from Gamma Ray Bursts in the Galaxy.
		Cosmic Rays and Gamma Ray Bursts From Microblazars.
		Cosmic Rays and Neutrinos from Gamma Ray Bursts.
	auger.cnrs.fr /grb.html (1027 words)

	Gamma Ray Bursters (Site not responding. Last check: 2007-11-07)
		Gamma-Ray bursters are powerful sources of Gamma-Ray emission that appear as short-duration "bursts" of gamma-ray emission.
		Most of these bursts have been recorded by the BATSE detector on the Compton Gamma Ray Observatory GRO.
		A single GRB may radiate in gamma-rays 3000 times as much energy as the Sun does in its whole lifetime.
	astrosun.tn.cornell.edu /academics/courses/astro201/gr_burst.htm (201 words)

	Satellites solve mystery of deep-space blasts / Dense neutron stars collide, producing gamma-ray bursters (Site not responding. Last check: 2007-11-07)
		Gamma ray bursters were accidentally discovered in the late 1960s by U.S. military satellites, which had been launched to detect radiation from secret Soviet nuclear weapons tests.
		Later, astronomers realized there are two basic types of bursters: "long bursts" and "short bursts." Long bursts last more than two seconds, and short bursts less than two seconds.
		Initially, astronomers assumed that all types of gamma-ray bursters were the same kind of phenomenon.
	sfgate.com /cgi-bin/article.cgi?f=/c/a/2005/10/06/MNGB9F365G1.DTL&type=science (709 words)

	GAMMA RAY BURSTERS AND SUPERNOVAS (Site not responding. Last check: 2007-11-07)
		GAMMA RAY BURSTERS AND SUPERNOVAS go together, at least in one instance.
		GRBs represent some of the most violent events in the universe and have been the subject of intense study and conjecture.
		One theory holds that GRBs are associated with supernovas (http://www.aip.org/enews/physnews/2000/split/512-3.html) This hypothesis is bolstered by new observations by the Chandra X-Ray Observatory of GRB 020813, a burster object discovered previously by the High-Energy Transient Explorer (HETE).
	www.phys.uni.torun.pl /~jkob/physnews/node17.html (103 words)

	Astronomy: Catching Gamma-Ray Bursters in the Act
		A gamma-ray burster seen April 25 was followed by a supernova in the same spot.
		Quicker response time should make it possible to catch dozens of bursters in the act and match more of them with objects that shine in wavelengths visible to the human eye.
		But the gamma-ray burster seen this year on April 25 in the southern constellation Telescopium was stranger by far, producing hundreds of thousands of times less peak gamma-ray energy.
	www.lbl.gov /Science-Articles/Archive/gamma-burster.html (611 words)

	Scientists catch another gamma-ray burster in visible light
		The team also pinned down GRB 990510, as it is designated, in the southern hemisphere in a constellation known as the Chamaeleon, at right ascension of 13h38m, and a declination of -80 deg.
		With a refined location, several southern observatories were aimed at GRB990510 in search of an visible-light counterpart (because GRB 990510 is in the Southern Hemisphere, it cannot be seen by the ROTSE array that captured the Jan. 28, 1999, burst).
		Observation details and announcements from the University of Amsterdam, Danish 1.54-meter La Silla telescope, the Astronomical Observatory of Brera, and the University of Warsaw 1.3-meter telescope, and the South African Astronomical Observatory.
	science.nasa.gov /newhome/headlines/ast18may99_1.htm (1178 words)

	HubbleSite - Gamma-Ray Burst Found to be Most Energetic Event in Universe - 5/6/1998
		A team of astronomers has announced that a recently detected gamma-ray burst was as bright as the rest of the universe, releasing a hundred times more energy than previously theorized.
		The team measured the distance to a faint galaxy from which the burst, designated GRB 971214, originated.
		This Hubble image of the GRB 971214 field was taken about four months after the burst, well after the afterglow had faded away.
	hubblesite.org /newscenter/newsdesk/archive/releases/1998/17 (192 words)

	Gamma Ray Bursts: Powerful Objects Remain a Mystery (Site not responding. Last check: 2007-11-07)
		Gamma Ray Bursters are so-named because they produce a phenomenal amount of very high-energy photons (gamma-rays) in a very short amount of time (seconds).
		Since their discovery years ago, very little progress has been made as to the nature of the gamma ray bursters, even though hundreds of different theories have been proposed.
		Understanding these objects, however, could provide critical keys to understanding the nature of dark matter in the Universe, or phase transitions in the Early Universe, or our own comet cloud, but right now are mysterious enough on their own.
	www.suite101.com /articles/article.cfm/585 (369 words)

	Science & Technology at Scientific American.com: The Brightest Explosions in the Universe -- [ ASTRONOMY ] -- Every ... (Site not responding. Last check: 2007-11-07)
		Before 1997, most of what we knew about GRBs was based on observations from the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma Ray Observatory.
		The January 1999 burst emitted gamma rays for a minute and a half.
		BeppoSAX was the first satellite to localize GRBs precisely and to discover their x-ray "afterglows." The afterglow appears when the gamma-ray signal disappears.
	www.sciam.com /article.cfm?chanID=sa006&articleID=00056F3D-4B5A-1DC8-AF71809EC588EEDF (908 words)

	Gamma-Ray Bursters Cross The
		They are powerful blasts of gamma- and X-radiation that come from all parts of the sky, but never from the same direction twice.
		The Synchrotron Shock Model predicts that the slope of the line that fits the lower energy part of the spectrum cannot be greater than -2/3.
		In a recently published edition of the Astrophysical Journal Letters Rob Preece and his collaborators from the University of Alabama examined over 100 bright bursts collected by the BATSE instrument on the Compton Gamma Ray Observatory and measured the slopes of their low-energy spectra.
	www.eurekalert.org /pub_releases/1998-10/NSFC-GBCT-131098.php (766 words)

	Physics News Update Number 423 - Story THE SCIENCE OF GAMMA RAY BURSTERS (Site not responding. Last check: 2007-11-07)
		Thus the object GRB990123 (with a redshift of 1.6) was glimpsed at optical wavelengths on January 23, 1999 at the crucial early stage of its eruption.
		Indeed this was the first time a GRB was detected optically while still belting out gammas.
		Judging by its gamma emissions it was either the most energetic GRB yet observed (if its energy were being spewed the same in all directions) or the observations constitute the first evidence for a beaming effect in GRB's.
	www.aip.org /enews/physnews/1999/split/pnu423-1.htm (171 words)

	Scientists witness visible light from a powerful gamma-ray burst
		The entire duration of the gamma-ray burst was only 110 seconds, but in that brief span of time Akerlof's team was able to do what had never been done before: follow the variations of visible light throughout the burst.
		The gamma ray and optical counterpart burst is near the constellation Corona Borealis.
		They also noticed a faint galaxy located close to the line of sight between the Earth and the burst source, but this galaxy does not appear to be related to the burst.
	science.nasa.gov /newhome/headlines/ast27jan99_1.htm (2092 words)

	Gamma-ray bursts: Introduction to a Mystery
		Lasting anywhere from a few milliseconds to several minutes, gamma-ray bursts (GRBs) shine hundreds of times brighter than a typical supernova and about a million trillion times as bright as the Sun, making them briefly the brightest source of cosmic gamma-ray photons in the observable Universe.
		GRBs are detected roughly once per day from wholly random directions of the sky.
		Until recently, GRBs were arguably the biggest mystery in high-energy astronomy.
	imagine.gsfc.nasa.gov /docs/science/know_l1/bursts.html (408 words)

	June 3, 2005, Hour Two: Gamma Ray Bursters / Space Elevator / Looking vs Seeing
		New research says that the more rare the object you're looking for is, the more likely you are to make a mistake when it finally appears.
		Plus, searching for the source of mysterious gamma ray bursters -- the most energetic events in the universe.
		New research says all gamma ray bursters may not be created in the same way.Call in with your questions and comments at 1-800-989-8255 (3-4 Eastern).
	www.sciencefriday.com /pages/2005/Jun/hour2_060305.html (326 words)

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