SourceDid You See the Supernova Last Week?
Shane McGlaun (Blog) - March 24, 2008 12:56 PM
There is an old adage that goes, “If a tree falls in a forest and no one is around to hear it, does it make a sound?"
A similar question was answered on Friday, “If a star blew up some 6 billion years ago when no one was on Earth, would anyone have seen it?”
The answer to that question is yes, we could see it, last week in fact. A star in a distant, previously unknown galaxy, exploded when the universe was about half its current age, some 6 billion years ago. This star was according to NASA about 40 times larger than our sun.
The explosion of the star resulted in a gamma ray burst that originated 7.5 billion light years away from Earth. It has taken these billions of years for the light from that explosion to reach Earth. NASA’s Swift satellite first detected the gamma rays at 2:12 a.m. Wednesday March 18, 2008.
The light from the explosion would have been visible by the naked eye if anyone had been outside to see last week. So bright was the light that it set a new record for the most distant object to be seen from Earth by the naked eye.
CNN quotes Neil Gehrels from NASA as saying, “Someone would have had to run out and look at it with a naked eye, but didn't.” The light would have appeared in the sky as bright as some of the stars in the handle of the Little Dipper constellation according to astronomer David Burrows. Burrow’s says that “This [explosion] is roughly halfway to the edge of the universe.”
Gehrels added that the explosion would have vaporized any planet nearby. Likely, the gamma ray burst would have eradicated anything in its path for thousands of light years. Earth dwellers had little to worry though, as the explosion took place so far away.
A single Polish observatory is the only verified organization to have taken a ground-based image of the gamma ray burst from the supernova.
Stellar Explosion Is Most Distant Object Visible to Naked Eye
SourceBy SPACE.com staff
posted: 21 March 2008
10:29 am ET
A powerful stellar explosion that has shattered the record for the most distant object visible to the naked eye was detected by NASA's Swift satellite on Wednesday.
The explosion, known as a gamma-ray burst, also ranks as the most intrinsically bright object in the universe ever observed by humans.
"It's amazing — we've been waiting for a flash this bright from a gamma-ray burst ever since Swift began observing the sky three years ago, and now we've got one that is so bright that it was visible to the naked eye even though its source is half-way across the universe," said David Burrows of Penn State University, who directs the continuing operation of Swift's X-ray telescope and the analysis of the data it collects.
Gamma-ray bursts are the most luminous explosions in the universe since the Big Bang and occur when massive stars run out of nuclear fuel. The stars' cores collapse to form black holes or neutron stars and release an intense burst of high-energy gamma-rays and jets of energetic particles.
The jets rip through space at nearly the speed of light, heating the surrounding interstellar gas like turbocharged cosmic blowtorches, often generating a bright afterglow.
"These optical flashes from gamma-ray bursts are the most extreme such phenomena that we know of," said Swift science team member Derek Fox, also of Penn State. "If this burst had happened in our galaxy, it would have been shining brighter than the Sun for almost a minute — sunglasses would definitely be advised."
Penn State astronomer and Swift team member Peter Meszaros said an unusual combination of circumstances may have made the burst's afterglow so exceptionally bright in the visible wavelengths of light.
"When the jet that formed during the explosion of the star slammed into the surrounding gas clouds, shock waves were generated that heated the jet," he explained. "The exceptional brightness of this burst requires the jet to have just the right combination of magnetic fields and velocity, which occurs very rarely."
Astronomers don't know for sure what made the burst, dubbed GRB 080319B, so bright, but further analysis of the event is under way. The burst could possibly have been more energetic than others, or the burst's energy may have been concentrated in a jet aimed directly at Earth.
The afterglow of GRB 080319B was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever recorded.
Astronomers have placed the star in the constellation Boötes. They have estimated it to be 7.5 billion light years away from Earth, meaning the explosion took place when the universe was less than half its current age and before Earth formed.
The most distant previous object that could be seen by the naked eye is the galaxy M33, a relatively short 2.9 million light-years from Earth.
The burst was detected by Swift at 2:12 EDT on March 19 and was one of five gamma-ray bursts detected that day, the same day that famed science fiction writer Arthur C. Clarke died.
"Coincidentally, the passing of Arthur C. Clarke seems to have set the universe ablaze with gamma-ray bursts," said Swift science team member Judith Racusin, a Penn State graduate student.