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Astrophysicists recently announced the discovery of 2 giants fastly growing gamma-ray bubbles at the centre of our galaxy. What caused them, might they threaten life on Earth and such an event ever occured before? I read that a gamma-ray burst aimed at the Earth could seriously jeopardize life on Earth. Thanks
Not likely. The most energetic astronomical explosions come from supernovas which occur when a massive star collapses into a neutron star or a black hole. Gamma ray bursts also emit large amounts of energy but small compared to a supernova. The last supernova observable on earth, 1987A, took place in a nearby dwarf galaxy, the Large Magellanic Cloud about 15 kiloparsec from Earth. Only a handful of neutrino events were seen in the huge water detector, Kamiokande, in Japan. One of the brightest recorded, now called the Crab nebula, occurred in 1054 and was noted by astronomers in China and Arabia. Its distance to the earth is about 2 kiloparsec. To give you an idea of the distance scale, the earth is about 8 kiloparsec from the center of the milky way, so the Crab supernova was reasonably close.
In order for such an explosion to seriously be harmful to the earth it would have to be very, very close to the earth. In sum, highly unlikely.
(published on 11/23/2010)
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