By Alex Galbraith , The Space Reporter | December 09, 2014
According to researchers, a gamma-ray burst very well may have caused a mass extinction over the course of the Earth’s history.
The name “gamma ray burst” sounds like something out of a comic book and the reality isn’t far off. These bursts are the most powerful explosions in the known universe, sending out a blast that is equivalent to all of the energy produced by the Sun in its 10 billion year lifetime. The only difference is the bursts do it over the span of a few minutes at most.
Gamma ray bursts are thought to be caused by an explosion of an extremely large star (called a “hypernova”) or the collision of two ultra-dense neutron stars. The hypernovas produce longer gamma ray bursts that go on for longer than two seconds. Neutron star collision causes the shorter bursts.
No gamma ray burst pointed at the Earth could fully penetrate the Earth’s atmosphere, but it would wreak havoc on the ozone layer and lead to a mass extinction. Long gamma ray bursts typically only happen in dwarf galaxies with sparse amounts of heavy elements, however, there are areas of the Milky Way that could spawn a burst.
Researchers at the Hebrew University in Jerusalem found that the likelihood of an extinction event on Earth triggered by gamma ray bursts was 50 percent in the past 500 million years, 60 percent in the past 1 billion years and more than 90 percent in the past 5 billion years.
The solar system is only around 4.6 billion years old, so it is very likely that the Earth was hit by a gamma ray burst at some point in its history. The researchers suggested that a burst may be responsible for one of the “Big 5″ extinction events.
The researchers went on to say that these bursts may help explain away a concept known as the Fermi Paradox, which questions why we haven’t found advanced civilizations in space considering the high probability that it exists. By the researchers estimates, life like the kind found on our planet can only safely develop in 10 percent of galaxies.
Other, more crowded galaxies would produce more regular gamma ray bursts, thereby increasing the likelihood of a developing planet getting blasted. And researchers add that any planets that harbor advanced civilizations could have only begun around 5 billion years ago. Before that, galaxies were too compact for a life-harboring planet to avoid blasts.
“This may be an explanation, or at least a partial one, to what is called the Fermi paradox or the ‘Big Silence,'” said lead study author Tsvi Piran. “Why we haven’t encountered advanced civilizations so far? The Milky Way galaxy is much older than the solar system and there was ample time and ample space — the number of planetary systems with conditions similar to Earth is huge — for life to develop elsewhere in the galaxy. So why we haven’t encountered advanced civilizations so far?”
http://thespacereporter.com/2014/12/gamma-ray-burst-may-have-caused-mass-extinction-on-earth/http://www.scienceclarified.com/Mu-Oi/Neutron.htmlhttp://www.livescience.com/49040-gamma-ray-burst-mass-extinction.html
