Hypernova

From Free net encyclopedia

A hypernova is a theoretical type of supernova produced when an exceptionally large star collapses at the end of its lifespan. In a hypernova, the core of the star collapses directly into a black hole and two extremely energetic jets of plasma are emitted from its rotational poles at nearly the speed of light. These jets emit intense gamma rays, and are a candidate explanation for gamma ray bursts. In recent years a flurry of observational data on gamma ray bursts significantly increased our understanding of these events.

Since stars sufficiently large to collapse directly into a black hole are quite rare, hypernovae should likewise be rare. It is estimated that a hypernova occurs in our galaxy every 200 million years.

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Hypothetical scenarios involving Earth

It has been theorized that the energy released by a hypernova relatively nearby might be capable of wiping out life on Earth. Scientists at NASA and the University of Kansas in 2005 released a study that says a mass extinction on Earth 450 million years ago, known as the Ordovician extinction, could have been triggered by a gamma-ray burst. Hitting the Earth for only ten seconds, a gamma ray outburst caused by a hypernova could deplete up to half of the atmosphere's protective ozone layer. With the ozone layer damaged, ultraviolet radiation from the Sun could kill much of the life on land and near the surface of oceans and lakes, and disrupt the food chain.

If hypernovae only occur in massive stellar objects at least 40 times the mass of our sun, then the Earth is completely safe from such an event. The closest hypernova candidate, Eta Carinae, is over 7,500 light years away.

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