Artist's illustration of a powerful gamma-ray burst, the most powerful type of explosion in the universe.
CREDIT: Dana Berry/NASA
The persistence of life on Earth may depend on massive explosions on the other side of the galaxy, according to a new theory that suggests powerful bursts of space radiation could have played a part in some of our planet's major extinction events.
The explosions — gamma-ray bursts thought to occur when two stars collide — can release tons of high-energy gamma-ray radiation into space. The researchers found that such blasts could be contributing to the depletion of the Earth's ozone layer. Disruption of the ozone layer lets ultraviolet light filter down to the surface of the Earth, where it can change organisms by mutating their genes.
Now, researchers are beginning to connect the timing of these gamma-ray bursts to extinctions on Earth that can be dated through the fossil record.
We find that a kind of gamma-ray burst — a short gamma-ray burst — is probably more significant than a longer gamma-ray burst," study researcher Brian Thomas of Washburn University, in Topeka, Kansas, said in a statement. "The duration is not as important as the amount of radiation." [Top 10 Strangest Things in Space]
The research will be presented Sunday (Oct. 9) at the Geological Society of America's annual meeting in Minneapolis.
Bursting out
Gamma-ray bursts come in two flavors: a longer, brighter burst and a "short-hard" burst, which lasts less than a second but seems to give off more radiation than a longer burst.
If such a burst were to happen inside the Milky Way, its effects on Earth would be much longer lasting. These bursts of radiation reach the Earth's atmosphere and cause free oxygen and nitrogen atoms to bang together, and some recombine into ozone-destroying compounds called nitrous oxides. Nitrous oxides in the atmosphere are long-lived; they keep destroying ozone until they fall out of the sky in rain drops.
The short bursts may be caused by fender-benders between stars, such as dense neutron stars or black holes colliding. The researchers were able to estimate that such stellar collisions probably happen about once every 100 million years in any given galaxy. At this rate, Earth would have been hit by several of these short-hard events over the course of its 4.5-billion-year history.
Life on Earth
Destruction of the ozone layer can have many effects on life on our planet. Radiation blasts on the world's plants and animals could wreak havoc on Earth's food webs and possibly lead to planetwide extinction events.
Improved and accumulated data collected by NASA's
SWIFT satellite, which catches gamma-ray bursts in action in other galaxies, is providing a better case for the power and threat of the short bursts to life on Earth. Researchers are also looking for evidence of past bursts, including special elements that are created only during radiation events hitting Earth, such as a heavy version of iron.
Thomas is now working with paleontologists to correlate levels of this heavy iron with evidence of extinction events in the fossil records.
"I work with some paleontologists, and we try to look for correlations with extinctions, but they are skeptical," Thomas said. "So if you go and give a talk to paleontologists, they are not quite into it. But to astrophysicists, it seems pretty plausible."
Powerful Space Explosion May Herald Star's Death By Black Hole
mages from NASA's Swift satellite were combined in this UV/optical/X-ray view of the explosion, which is known as GRB 110328A. The blast was detected in X-rays, which were collected on March 28.
CREDIT: NASA/Swift/Stefan Immler
A huge, powerful star explosion detonated in deep space last week — an ultra-bright conflagaration that has astronomers scratching their heads over exactly how it happened.
The explosion may be the death cry of a star as it was ripped apart by a black hole, scientists said. High-energy radiation continues to brighten and fade from the March 28 blast's location, about 3.8 billion light-years from Earth in the constellation Draco. [Image of the space explosion]
Astronomers say they've never witnessed an explosion so bright, long-lasting and variable before, according to NASA officials.
The explosion looks like a gamma-ray burst — the most powerful type of explosion in the universe, which usually mark the destruction of a massive star — but the flaring emissions from these dramatic events never last more than a few hours, researchers said.
"We know of objects in our own galaxy that can produce repeated bursts, but they are thousands to millions of times less powerful than the bursts we are seeing now," said Andrew Fruchter, of the Space Telescope Science Institute in Baltimore, in a statement today (April 7). "This is truly extraordinary."
Massive explosion in space
Scientists are using several NASA space observatories, working in concert, to study the massive blast.
The space explosion was detected on March 28 when an instrument on NASA's Swift satellite detected an X-ray eruption, the first in a series of powerful blasts. The Swift observatory determined a rough position for the explosion, which scientists are now calling the gamma-ray burst (GRB) 110328A. [Video: What Makes the Brightest Flash in the Universe?]
After Swift's discovery, an image taken by the Hubble Space Telescope on Monday (April 4) pinpointed the exact source of the blast — the center of a small galaxy in the Draco constellation. That same day, astronomers used the Chandra X-ray Observatory to make a four-hour exposure of the puzzling source.
Although research is ongoing, astronomers say that the unusual explosion likely arose when a star wandered too close to its galaxy's central black hole. Intense tidal forces probably tore the star apart, and the infalling gas continues to stream toward the black hole.
According to this model, the spinning black hole formed an outflowing jet, which is blasting powerful X-rays and gamma rays in our direction, researchers said.
"The fact that the explosion occurred in the center of a galaxy tells us it is most likely associated with a massive black hole," said Neil Gehrels, the lead scientist for Swift at NASA's Goddard Space Flight Center, in a statement. "This solves a key question about the mysterious event."
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