Are Gamma-Ray Bursts Responsible for the Extinction on the Earth?

Gamma­-Ray Bursts – the Strongest Explosions in the Universe

The new study said that extremely powerful stellar explosions, known as Gamma-Ray Bursts, could be the reason behind the mass extinction events on the Earth. These events may also have prevented life from being developed until about 5 billion years ago and also pushed the locations, where life could possibly occur, to the edges of the galaxies. The lead study author Tsvi Piran, a physicist at the Hebrew University in Jerusalem said, that these bursts could also explain the so-called Fermi paradox – the apparent contradiction between high probability of the existence of extraterrestrial civilizations and the lack of evidence for it.

The Gamma-ray Bursts (GRBs) are the most intense form of explosion in the Universe that we know. The bursts are capable of producing as much energy as our Sun does in its entire lifetime in just few seconds. The scientists believe, that they are caused by giant stars which explode or, another reason could be that collisions are happening between stars known as neutron stars.

Gamma-Ray bursts; photo credit: NASA Goddard Space Flight Center, CC BY 2.0

If such an event like this would happen close enough to the Earth, planet would be in serious trouble. It would destroy ozone layer, which would expose us to the UV rays, which would kill the majority of the life. The thread of this happening is minimal (but not completely out of the table), because the GRBs are happening in galaxies, which are very different from our own. These types of galaxies are known as low metallicity galaxies, galaxies with low concentrations of metals and other heavy elements. And Milky Way is a high metallicity galaxy.

Even though GRBs are very rare, they do actually happen as long Gamma-Ray Bursts in galaxies like ours. In Milky Way the rate of explosion is around one-tenth that if the average rate in the Universe. The results of this study also confirmed, that there was a 60 percent chance, that GRBs was the trigger of a mass extinction event in the past 1 billion years and 90 percent that this happened within 5 billion years. This means that GRBs could be the reason behind the event known as Ordovician extinction.

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The study also found out, that the center of the Milky Way is more likely to have one of the GRBs, because of the high density of the stars in this region, which is why the life is in the outside part of the galaxy.

In the video below, you can see NASA’s Swift Gamma-Ray Bursts exploring satellite discovering bursts and locations of all Gamma-Ray Bursts discovered up till its 500th burst in April 13,2010. Till now it is more than 900 GRBs. Swift’s main job is to quickly localize each gamma-ray burst, report its position so that scientists can immediately conduct follow-up observations, and then study the burst using its X-ray and Ultraviolet/Optical telescopes. Some bursts that are worth mentioning are identified in the video.

source: physics.aps.org

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