Brightest Explosion In the Universe Ever Seen Defies Astronomy Theories

[Buster's Uncle]

Brightest Explosion In the Universe Ever Seen Defies Astronomy Theories
SPACE.com
By Denise Chow 6 hours ago






A mysterious blast of light spotted earlier this year near the constellation Leo was actually the brightest gamma-ray burst ever recorded, and was triggered by an extremely powerful stellar explosion, new research reports.

On April 27, several satellites — including NASA's Swift satellite and Fermi Gamma-ray Space Telescope — observed an unusually bright burst of gamma radiation. The explosion unleashed an energetic jet of particles that traveled at nearly the speed of light, researchers said.

"We suddenly saw a gamma-ray burst that was extremely bright — a monster gamma-ray burst," study co-author Daniele Malesani, an astrophysicist at the Niels Bohr Institute at the University of Copenhagen in Denmark, said in a statement. "This [was] one of the most powerful gamma-ray bursts we have ever observed with the Swift satellite."

The gamma-ray burst was described in a series of studies published online today (Nov. 21) in the journal Science.

Gamma-ray bursts, or GRBs, are the most powerful type of explosions in the universe and typically mark the destruction of a massive star. The original stars are too faint to be seen, but the supernova explosions that signal a star's death throes can cause violent bursts of gamma radiation, researchers said.

Gamma-ray bursts are usually short but extremely bright. Still, ground-based telescopes have a tough time observing them because Earth's atmosphere absorbs the gamma radiation.



A gamma-ray burst that exploded in April 2013 is the most luminous object in the field


The extremely bright gamma-ray burst seen earlier this year, officially dubbed GRB 130472A, occurred in a galaxy 3.6 billion light-years away from Earth, which, though still far away, is less than half the distance at which gamma-ray bursts have previously been seen. This closer proximity to Earth enabled astronomers to confirm for the first time that one object can simultaneously create a powerful GRB and a supernova explosion.

"We normally detect GRBs at great distance, meaning they usually appear quite faint," study co-author Paul O'Brien, an astronomer at the University of Leicester in the United Kingdom, said in a statement. "In this case, the burst happened only a quarter of the way across the universe — meaning it was very bright. On this occasion, a powerful supernova was also produced — something we have not recorded before alongside a powerful GRB — and we will now be seeking to understand this occurrence."

The jet produced by the gamma-ray burst was formed when a massive star collapsed on itself and created a black hole at its center. This generated a blast wave that caused the stellar remnants to expand, producing a glowing shell of debris that was observed as an extremely bright supernova explosion.

After analyzing properties of the light produced by the gamma-ray burst, scientists determined that the original star was only three to four times the size of the sun, but was 20 to 30 times more massive. This extremely compact star was also rapidly rotating, the researchers said.

The GRB was the brightest and most energetic ever witnessed and triggered dynamic internal and external shock waves that are still not well understood. Though scientists have a clearer view of the violent explosion, mysteries remain. For instance, space telescopes detected more photons and more high-energy gamma-rays than theoretical models predicted for a gamma-ray burst of this magnitude.

Researchers are still investigating why the energy levels seen with GRB 130472A do not quite match predictions from existing models of gamma-ray bursts. Their results could lead to more refined theories about how particles are accelerated, which could help astronomers better predict the behavior of cosmic events.

"The really cool thing about this GRB is that because the exploding matter was traveling at [nearly] the speed of light, we were able to observe relativistic shocks," study co-author Giacomo Vianello, a postdoctoral scholar at Stanford University in California, said in a statement. "We cannot make a relativistic shock in the lab, so we really don't know what happens in it, and this is one of the main unknown assumptions in the model. These observations challenge the models and can lead us to a better understanding of physics."


http://news.yahoo.com/brightest-explosion-universe-ever-seen-defies-astronomy-theories-191012403.html

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It's the Beyonder!

[Buster's Uncle]

'Monster' cosmic blast zipped harmlessly by Earth
Associated Press
By SETH BORENSTEIN 5 hours ago



This image provided by NASA's Goddard Space Flight Center shows an artists rendering on how a gamma ray burst occurs with a massive star collapsing and creating a black hole and beaming out focused and deadly light and radiation bursts. Astronomers and space telescopes in April 2013 saw the biggest and brightest cosmic explosion ever witnessed, a large gamma ray burst. (AP Photo/NASA Goddard Space Flight Center)



WASHINGTON (AP) — Astronomers call it the monster. It was the biggest and brightest cosmic explosion ever witnessed. Had it been closer, Earth would have been toast.

Orbiting telescopes got the fireworks show of a lifetime last spring when they spotted what is known as a gamma ray burst in a far-off galaxy.

The only bigger display astronomers know of was the Big Bang — and no one, of course, was around to witness that.

"This burst was a once-in-a-century cosmic event," NASA astrophysics chief Paul Hertz said at a news conference Thursday.

But because this blast was 3.7 billion light-years away, mankind was spared. In fact, no one on Earth could even see it with the naked eye.

A gamma ray burst happens when a massive star dies, collapses into a brand-new black hole, explodes in what's called a supernova and ejects energetic radiation. The radiation is as bright as can be as it travels across the universe at the speed of light.

A planet caught in one of these bursts would lose its atmosphere instantly and would be left a burnt cinder, astronomers say.

Scientists might be able to detect warning signs of an impending gamma ray burst. But if a burst were headed for Earth — and the chances of that happening are close to zero, astronomers say — there wouldn't be anything anybody could do about it.

NASA telescopes in orbit have been seeing bursts for more than two decades, spotting one every couple of days. But this one, witnessed on April 27, set records, according to four studies published Thursday in the journal Science.

It flooded NASA instruments with five times the energy of its nearest competitor, a 1999 blast, said University of Alabama at Huntsville astrophysicist Rob Preece, author of one of the studies.

It started with a star that had 20 to 30 times the mass of our sun but was only a couple of times wider, so it was incredibly dense. It exploded in a certain violent way.

In general, gamma ray bursts are "the most titanic explosions in the universe," and this one was so big that some of the telescope instruments hit their peak, Preece said. It was far stronger and lasted longer than previous ones.

"I call it the monster," Preece said. In fact, one of the other studies, not written by Preece, used the word "monster" in its title, unusual language for a scientific report.

One of the main reasons this was so bright was that relative to the thousands of other gamma ray bursts astronomers have seen, the monster was pretty close by cosmic standards. A light-year is almost 6 trillion miles.

Most of the bursts NASA telescopes have seen have been twice as distant as this one. Other explosions could be this big, but they are so much farther away, they don't seem so bright when they reach Earth, the studies' authors say.

Astronomers say it is incredibly unlikely that a gamma ray burst — especially a big one like this — could go off in our galaxy, near us. Harvard's Avi Loeb, who wasn't part of the studies, put the chances at less than 1 in 10 million.

Our galaxy doesn't have many of the type of star that lends itself to gamma ray bursts, said Charles Dermer, a co-author of the studies and an astrophysicist at the U.S. Naval Research Laboratory.

"The chance of anything happening and being dangerous is virtually nil," Dermer said.

Also, because a burst is concentrated like a focused searchlight or a death beam, it has to be pointing at you to be seen and to be dangerous.

"Either it's pointed at us or it's not," Preece said. "If it's not, yay! Civilization survives and we see maybe a supernova. If it were pointed at us, then it matters very much how far away it is in our galaxy. If it's in our local arm, well, we had a good run."

Some theorize that a mass extinction on Earth 450 million years ago was caused by a gamma ray burst in a nearby part of our galaxy, but Dermer said that's unlikely.

We don't see gamma ray bursts from the surface of Earth because the atmosphere obscures them and because most of their light is the type we cannot see with our eyes. That's why NASA has satellites that look for them.

This burst was so bright telescopes on Earth saw a brief flash in the constellation Leo.

For scientists, this was a wow moment.

"These are really neat explosions," said Peter Michelson, a Stanford physicist who is the chief scientist for one of the instruments on a NASA gamma ray burst-spotting telescope. "If you like fireworks, you can't beat these. Other than the Big Bang itself, these are the biggest there are."

The burst "is part of the cycle of birth and life and death in the universe," Michelson said. "You and I are made of the stuff that came from a supernova."

___

Online:

Journal Science: http://www.sciencemag.org

NASA: http://1.usa.gov/1dlvvy3


http://news.yahoo.com/monster-cosmic-blast-zipped-harmlessly-earth-191349814.html