Article Posted on : - Mar 26, 2011

LONDON (PTI): Despite years of investigation, scientists have not yet been able to find any life beyond our planet. Now, some astronomers say the destructive force of exploding stars might have wiped out aliens.

In particular, a phenomenon known as a white dwarf hypernova could have sucked alien life into a black hole, they believe.

When a large white dwarf star, a collapsed remnant of an elderly star, becomes unstable and explodes, it is called hypernova which scientists believe might have occurred several times over millions of years, the Daily Mail reported.

They also believe there is possibility that life on Earth too could be wiped out by the process of gamma ray bursts.

Intense gamma radiation produces of nitrous oxides that could perhaps destroy the ozone layer.

It is possible that such a phenomenon may occur "soon" on the timescales familiar to astronomers, said Dr Edward Sion from Villanova University in Pennsylvania.

But such an event is very unlikely to occur in the next few hundred years, he conceded.

Hypernovas are considered as the explosion of all hypergiants, or stars with a solar mass of between 100 and 300 times that of the sun.

A decaying isotope of nickel is believed to provide much of a hypernova's light. A more impressive light show yet is produced when two collapsing white dwarfs, each the size of Earth, merge.

The process also produces the phenomenon known as a stellar-mass black hole, a permanent giant gap in the galaxy.

This is produced by gravitational collapse, is the inward fall of the star's body due to force of the explosion.

The collapse of a star is a natural process that occurs when all stellar energy sources are exhausted.

If the mass of the collapsing part of the star is below a certain critical value, the end product is a compact star, either a white dwarf or a neutron star.

But if the collapsing star has a mass exceeding this limit, the collapse will continue forever and form a black hole and astronomers believe that any collapsing star with solar mass above 0.7 will form a black hole.

A hypernova could cause serious harm to Earth, but no known hypergiant is located close enough to our planet to pose a direct threat, the researchers said.