Record-breaking Gamma-ray Burst

[Divinity]

http://www.astronomy.com/asy/default.aspx?c=a&id=7414


Satellite discovers record-breaking gamma-ray burst
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Swift satellite found the farthest burst ever detected.
Provided by NASA

GRB 080913 exploded September 13 at a whopping distance of 12.8 billion light-years away in the constellation Eridanus.

The box indicates the sky area shown in the Swift image. DSS/STScI/AURA

September 22, 2008
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NASA's Swift satellite has found the most distant gamma-ray burst (GRB) ever detected. The blast, designated GRB 080913, arose from an exploding star 12.8 billion light-years away.

"This is the most amazing burst Swift has seen," says the mission's lead scientist Neil Gehrels at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It's coming to us from near the edge of the visible universe."

Because light moves at finite speed, looking farther into the universe means looking back in time. GRB 080913's "lookback time" reveals that the burst occurred less than 825 million years after the universe began.

The star that caused this shot seen across the cosmos died when the universe was less than one-seventh its present age.

"This burst accompanies the death of a star from one of the universe's early generations," says Patricia Schady of the Mullard Space Science Laboratory at University College London, who is organizing Swift observations of the event.



This image merges the view through Swift's UltraViolet and Optical Telescope, which shows bright stars, and its X-ray Telescope, which captures the burst (orange and yellow). NASA/Swift/Stefan Immler [View Larger Image]Gamma rays from the far-off explosion triggered Swift's Burst Alert Telescope at 1:47 A.M. EDT on September 13. The spacecraft established the event's location in the constellation Eridanus and quickly turned to examine the spot. Less than 2 minutes after the alert, Swift's X-Ray Telescope began observing the position. There, it found a fading, previously unknown X-ray source.

Astronomers on the ground followed up as well. Using the 7.2-foot (2.2 meters) telescope at the European Southern Observatory in La Silla, Chile, a group led by Jochen Greiner at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, captured the bursts fading afterglow.

The telescope's software listens for alerts from Swift and automatically slewed to the burst position. Then, the team's Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) simultaneously captured the waning light in seven wavelengths.

"Our first exposure began just 1 minute after the X-Ray Telescope started observing," Greiner says.



GRB 080913 can't be seen in one of GROND's optical filters (left), but appears in another (right). The sudden appearance of objects at longer wavelengths indicates great distance. MPE/GROND [View Larger Image]In certain colors, the brightness of a distant object shows a characteristic drop caused by intervening gas clouds. The farther away the object is, the longer the wavelength where this fade-out begins. GROND exploits this effect and gives astronomers a quick estimate of an explosion's shift toward the less energetic red end of the electromagnetic spectrum, or redshift, which suggests its record-setting distance.

An hour and a half later, as part of Greiner's research, the Very Large Telescope at Paranal, Chile, targeted the afterglow. Analysis of the spectrum with Johan Fynbo of the University of Copenhagen established the blasts redshift at 6.7 — among the most distant objects known.

GRBs are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, gas jets — driven by processes not fully understood — punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates bright afterglows.

The previous record holder was a burst with a redshift of 6.29, which placed it 70 million light-years closer than GRB 080913.

Swift, launched in November 2004, has had a banner year. In March, the satellite detected the brightest GRB, which was visible to the human eye despite occurring billions of light-years away. And in January, the spacecraft's instruments caught the first X-rays from a new supernova days before optical astronomers saw the exploding star.

[junglelord]

GRBs are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, gas jets — driven by processes not fully understood — punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates bright afterglows.

Well thats debateable. I would imagine a plasma instability and a huge Z Pinch would also account for such gamma ray bursts. Infact I know it does and the forces are very well understood.

[Steve Smith]

In Space No One Can Hear You Scream

http://www.thunderbolts.info/tpod/2008/ ... scream.htm

[webolife]

P'raps not, but another possibility which could attest to the GRB object being closer to our galactic neighborhood is the object's spin/rotation rate. The burst, as a vector tug, occupies a baseline of visibility which, if crossing our view over a brief period of time, would yield light lines at different locations in the spectrum [I don't say wavelengths] during that time of our encounter with it. In other words, the brief period of visibility would have been from a single GRB event distributed over time mostly as a result of the object rotating. A possible analogy... the spinning vectoral GRB "tug" like a swinging baseball bat, intersects with our earth's eye like a baseball, a brief moment of elasticity during impact when the ball is experiencing the maximum pressure of the bat, then the encounter is past. I predict a degree of symmetry in the timing and distribution of the flashes, as well as a direct correlation with the light spectrum. I would expect that some of the light flashes were missed prior to the GRB and only the afterflashes were caught due to the constraints of the observing stations.

[MGmirkin]

P'raps not, but another possibility which could attest to the GRB object being closer to our galactic neighborhood

Or this...

(Hibernating "Stellar Magnet" found? Local or Distant?)
http://thunderbolts.info/forum/phpBB3/v ... f=3&t=1039

This weird object initially misled its discoverers as it showed up as a gamma-ray burst, suggesting the death of a star in the distant Universe. But soon afterwards, it exhibited some unique behaviour that indicates its origin is much closer to us.

Regards,
~Michael Gmirkin

[StefanR]

Lightning and Terrestrial Gamma-Ray Flashes (TGFs)
http://www.thunderbolts.info/forum/phpB ... =415#p3965

Phew, that was close!

[Divinity]

Clever Group

[MGmirkin]

Lightning and Terrestrial Gamma-Ray Flashes (TGFs)
http://www.thunderbolts.info/forum/phpB ... =415#p3965

Phew, that was close!

Thanks for the nudge... I'd actually forgotten all about that thread! ;o]

Good stuff!
~Michael Gmirkin

[StefanR]

An asymmetric distribution of positrons in the Galactic disk revealed by gamma-rays

Gamma-ray line radiation at 511 keV is the signature of electron-positron annihilation. Such radiation has been known for 30 years to come from the general direction of the Galactic Centre, but the origin of the positrons has remained a mystery. Stellar nucleosynthesis accreting compact objects and even the annihilation of exotic dark-matter particles have all been suggested. Here we report a distinct asymmetry in the 511-keV line emission coming from the inner Galactic disk (~10-50° from the Galactic Centre). This asymmetry resembles an asymmetry in the distribution of low mass X-ray binaries with strong emission at photon energies >20 keV ('hard' LMXBs), indicating that they may be the dominant origin of the positrons. Although it had long been suspected that electron-positron pair plasmas may exist in X-ray binaries, it was not evident that many of the positrons could escape to lose energy and ultimately annihilate with electrons in the interstellar medium and thus lead to the emission of a narrow 511-keV line. For these models, our result implies that up to a few times 1041 positrons escape per second from a typical hard LMXB. Positron production at this level from hard LMXBs in the Galactic bulge would reduce (and possibly eliminate) the need for more exotic explanations, such as those involving dark matter.

http://sci.esa.int/science-e/www/object ... ctid=42203