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Hypernova Erupts as Global Telescopes Scramble
An anonymous reader writes "The remarkable Robotic Optical Transient Search Experiment [ROTSE] telescopes have tracked a 2 billion year old hypernova, from which an intense gamma ray burst reached earth on March 29. From Carl Akerlof, the ROTSE investigator: "The optical brightness of this gamma ray burst is about 100 times more intense than anything we've ever seen before." To underscore how the sun never rises on this automated telescope network, the observations switched rapidly from New South Wales in Australia back to Fort Davis, Texas, over a 12 hour burnout of the collapsing black hole."
** KARMA WHORE MODE: OFF **
Hypernova Blast:
Global Chase Ensues
based on U. Michigan release
Two billion years ago, in a far-away galaxy, a giant star exploded, releasing almost unbelievable amounts of energy as it collapsed to a black hole. The light from that explosion finally reached Earth at 6:37 a.m. EST on March 29, igniting a frenzy of activity among astronomers worldwide. This phenomenon has been called a hypernova, playing on the name of the supernova events that mark the violent end of massive stars.
With two telescopes separated by about 110 degrees longitude, the Robotic Optical Transient Search Experiment (ROTSE) will have one of the most continuous records of this explosion.
The changing intensity of a gamma-ray burst. On the left is an image of the gamma ray sky showing the burst becoming the brightest object. On the right is a plot of the changing brightness with time. The first gamma-ray burst was seen in the year 1967 (although it was not reported to the world until 1973) by satellite-borne detectors intended to look for violations of the Nuclear Test Ban Treaty. Credit: BATSE
"The optical brightness of this gamma ray burst is about 100 times more intense than anything we've ever seen before. It's also much closer to us than all other observed bursts so we can study it in considerably more detail," said Carl W. Akerlof, an astrophysicist in the Physics Department at the University of Michigan.
Contrary to visible light, gamma rays are non-thermal meaning that they are not produced in hot celestial bodies like the sun. Gamma rays occur in exceptional circumstances such as in the aftermath of a stellar explosion, in the vicinity of black holes, or at the core of active galaxies.
Just recently, the ROTSE group commissioned two optical telescopes in Australia and Texas and were waiting for the first opportunities to use the new equipment. The burst was promptly detected by NASA's Earth orbiting High-Energy Transient Explorer (HETE-2) but human intervention was required to find the exact location.
Despite sporadic clouds and rainstorms in Australia, the ROTSE instrument at Siding Spring Observatory in northern New South Wales was able to record the decaying light from the blast. Twelve hours later, the second ROTSE telescope in Fort Davis, Texas was picking up the job of monitoring this spectacular explosion.
"During the first minute after the explosion it emitted energy at a rate more than a million times the combined output of all the stars in the Milky Way. If you concentrated all the energy that the sun will put out over its entire 9 billion-year life into a tenth of a second, then you would have some idea of the brightness," said Michael Ashley, faculty member in the astrophysics and optics department at the University of New South Wales and a member of the ROTSE team.
Given that the history of astronomy goes back centuries, observations in the gamma spectrum are really among the newest areas in celestial research. The high-energy light is swallowed by the earth's atmosphere yet the light cannot be captured with conventional lenses or mirrors. Special detectors in satellites and high altitude research rockets register gamma rays with energies of up to around ten billion electron volts.
Gamma rays occur in exceptional circumstances such as in the aftermath of a stellar explosion, in the vicinity of black holes, or at the core of active galaxies. Credit: NASA
Fortunately for life on earth, a gamma particle from the universe does not penetrate to the earth's surface, but if it flies past an atomic nucleus within the earth's atmosphere, the gamma particle can transform itself into an electron and its (positive) antiparticle, a positron. During its journey through the air, this pair comes across more atomic nuclei and a gamma quantum is generated which then once again hits atomic nuclei. Thus, a single cosmic gamma particle creates roughly a thousand secondar
However, it's much easier just to put the telescope in orbit around the earth. Without atmospheric scattering, the telescope can be aimed close to the sun. That's one of the advantages of Hubble over any terrestrial telescope.
Panurge has posted for the last time. Thanks for the positive moderations.
'Contrary to visible light, gamma rays are non-thermal meaning that they are not produced in hot celestial bodies like the sun. Gamma rays occur in exceptional circumstances such as in the aftermath of a stellar explosion, in the vicinity of black holes, or at the core of active galaxies'
This is of course not true - gamma rays are produced in many places, among other things by Radium, if my memory serves me. And the Sun does indeed produce gamma rays are essentially just high energy photons, just like visible light (and radio waves, for that matter) with 'high energy'. Electromagnetic radiation is quantified in 'packets' called photons, and it is mostly a metter of taste whether you call them radio waves, microwaves, light, X-rays or gamma rays. There's an upper for gamma photons by the way (sort of): a photon with very high energy will tend to 'split' and form a pair consisting of an electron and a positron, which then annihilate in a burst of photons.