Article Posted on : - Apr 07, 2011

In this artist's conception, the reborn star is shown with a hypothetical world.

CAMBRIDGE (BNS): Astronomers have come across a pair of white dwarf stars revolving around each other and in the process of colliding to be reborn as a single star in few million years from now.

The newly spotted binary star system, designated SDSS J010657.39 – 100003.3, is located about 7,800 light-years away in the constellation Cetus in Milky Way. It consists of two white dwarfs, a visible star and an unseen companion whose presence is betrayed by the visible star’s motion around it.

The white dwarfs are swirling around each other once in every 39 minutes.

This is the shortest-period pair of white dwarfs now known, according to the researchers at the Harvard-Smithsonian Center for Astrophysics who have made the discovery.

“These stars have already lived a full life. When they merge, they'll essentially be 'reborn' and enjoy a second life,” said Smithsonian astronomer Mukremin Kilic, lead author on the paper announcing the discovery.

Out of the 100 billion stars in the Milky Way, only a handful of merging white dwarf systems are known to exist. The latest discovery will be the first of the group to merge and be reborn, according to the researchers.

Of the two dying stars revolving each other, one weighs about 17 percent as much as the Sun, while the second white dwarf weighs 43 per cent as much. Astronomers believe that both are made of helium.

While orbiting each other from a distance of 140,000 miles – less than the distance between Earth and Moon – the stars complete one orbit every 39 minutes at a speed of 270 miles per second.

The fate of these stars is already sealed. Because they wheel around so close to each other, the white dwarfs stir the space-time continuum, creating expanding ripples known as gravitational waves. Those waves carry away orbital energy, causing the stars to spiral closer and closer together.

In about 37 million years, they will collide and merge, say the astronomers.

When some white dwarfs collide, they explode as a supernova. However, to explode, the two combined have to weigh 40 percent more than our Sun.

This new-found white dwarf pair isn’t heavy enough to go supernova. Instead, they will experience “a second life”. The merged remnant will begin fusing helium and shine like a normal star once more.

“We will witness starlight reborn,” the researchers say.