GammaRayBurstWords
Gamma ray bursts don’t loiter, and neither can the people who hunt them. That’s why astronomer Andy Fruchter’s cell phone rings every time one of these cosmic bursts – packed with the energy of a trillion suns – explodes in outer space. Though the origin of gamma ray bursts (GRBs) has eluded understanding since the 1960s, when scientists scanning the sky for elicit nuclear tests first witnessed these powerful explosions and miscontrued them for Russian bombs, Fruchter’s recent attention to cosmic detail has filled in a gap in the GRB mystery: what kinds of galaxies these massive explosions occur in.
Along with other astronomers from the Space Telescope Science Institute in Baltimore, Fruchter collected Hubble Telescope images which prove that long gamma ray bursts only occur in“scruffy environs.” This means there will be no mass exctinction of humans from cosmic GRBs anytime soon; our home galaxy, highly-evolved and metal-rich, is anything but scruffy. More importantly, though, Fruchter’s work co-localizes the occurrence of GRBs with supernovae, a second type of extremely energetic explosion.
Gamma ray bursts and supernovae occur at almost the same moment in time, in a quick and powerful one-two blow. Both result from the collapse of a massive star, with supernovae preceeding GRBs on the celestial timeline. “One would expect the two events to form in similar environments, too” Fruchter explains. But his Hubble images show that they don’t. In fact, the presence of a supernova doesn’t always indicate that a GRB will follow. To understand why the two aren’t always co-localized, Fruchter and his colleagues compared the locations – or, the galaxies- where GRBs and supernovae go off. They found that GRBs require a different set of characteristics from their host galaxies. The two explosions live in every different environments.
Though all GRBs are probably formed in supernovae, not all supernovae produce GRBs. Fruchter observed that if a supernova occurs in a massive galaxy, one which is aged, this supernova will not go on to produce a burst. He attributes this to the high metallicity characteristic of older galaxies, where metal ions have had years to accumulate, and suggests that GRBs can only be produced by supernovae in galaxies with low metal levels. Metallicity inhibits GRBS in two ways. First, metal ions in the atmosphere absorb emissions, or the gas jets constituting a GRB, and this smothers the burst. Second, the magnetic field generated by the metal ions opposes and slows the rapid spin needed to generate a GRB.
“Some supernova would like to produce GRBs,” explained Fruchter, “but they can’t.” These are the supernova seen in massive, metal-rich, evolved galaxies, like ours. Fruchter joked that “one of the conclusions of this study is ‘Relax!’ ” But even though we don’t have to worry about GRBs going off in our galaxy, we can still observe these massive explosions from Earth.
NASA employs a special spacecraft, known as Swift, to capture GRB images. They are difficult to capture, though. GRBs last only a few seconds – minutes at most- and occur randomly from all directions in the sky. To find them, the Swift spacecraft scans the sky. Its telescopes are designed to automatically detect the first flash of an explosion and then target that event as quickly as possible- usually in under a minute. It approximates GRB positions so that other telescopes, like the Hubble, can follow up and obtain pictures of the afterglow. Fruchter emphasized the difficulty of capturing such images. “There are well over 1000 gamma ray bursts known,” he explained, “but only 40 or so for which we have a good image.”
While charting these explosions has been difficult, Fruchter knows how to increase his odds. “My cell phone makes a really obnoxious noise, that I can’t ignore, if a gamma ray burst goes off” he laughed, pulling his phone from his pocket. Fruchter has followed the call of GRBs, elucidating their origins, and now we are all one step closer to understanding they mysteries surrounding these majestic explosions.
.MGW.
Along with other astronomers from the Space Telescope Science Institute in Baltimore, Fruchter collected Hubble Telescope images which prove that long gamma ray bursts only occur in“scruffy environs.” This means there will be no mass exctinction of humans from cosmic GRBs anytime soon; our home galaxy, highly-evolved and metal-rich, is anything but scruffy. More importantly, though, Fruchter’s work co-localizes the occurrence of GRBs with supernovae, a second type of extremely energetic explosion.
Gamma ray bursts and supernovae occur at almost the same moment in time, in a quick and powerful one-two blow. Both result from the collapse of a massive star, with supernovae preceeding GRBs on the celestial timeline. “One would expect the two events to form in similar environments, too” Fruchter explains. But his Hubble images show that they don’t. In fact, the presence of a supernova doesn’t always indicate that a GRB will follow. To understand why the two aren’t always co-localized, Fruchter and his colleagues compared the locations – or, the galaxies- where GRBs and supernovae go off. They found that GRBs require a different set of characteristics from their host galaxies. The two explosions live in every different environments.
Though all GRBs are probably formed in supernovae, not all supernovae produce GRBs. Fruchter observed that if a supernova occurs in a massive galaxy, one which is aged, this supernova will not go on to produce a burst. He attributes this to the high metallicity characteristic of older galaxies, where metal ions have had years to accumulate, and suggests that GRBs can only be produced by supernovae in galaxies with low metal levels. Metallicity inhibits GRBS in two ways. First, metal ions in the atmosphere absorb emissions, or the gas jets constituting a GRB, and this smothers the burst. Second, the magnetic field generated by the metal ions opposes and slows the rapid spin needed to generate a GRB.
“Some supernova would like to produce GRBs,” explained Fruchter, “but they can’t.” These are the supernova seen in massive, metal-rich, evolved galaxies, like ours. Fruchter joked that “one of the conclusions of this study is ‘Relax!’ ” But even though we don’t have to worry about GRBs going off in our galaxy, we can still observe these massive explosions from Earth.
NASA employs a special spacecraft, known as Swift, to capture GRB images. They are difficult to capture, though. GRBs last only a few seconds – minutes at most- and occur randomly from all directions in the sky. To find them, the Swift spacecraft scans the sky. Its telescopes are designed to automatically detect the first flash of an explosion and then target that event as quickly as possible- usually in under a minute. It approximates GRB positions so that other telescopes, like the Hubble, can follow up and obtain pictures of the afterglow. Fruchter emphasized the difficulty of capturing such images. “There are well over 1000 gamma ray bursts known,” he explained, “but only 40 or so for which we have a good image.”
While charting these explosions has been difficult, Fruchter knows how to increase his odds. “My cell phone makes a really obnoxious noise, that I can’t ignore, if a gamma ray burst goes off” he laughed, pulling his phone from his pocket. Fruchter has followed the call of GRBs, elucidating their origins, and now we are all one step closer to understanding they mysteries surrounding these majestic explosions.
.MGW.
posted by Meagan G at
2:14 PM
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