Supernova birth seen for first time by astronomers

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Washington, May 22 : Astronomers have observed the death of a star for the first time in the form of a stellar explosion, which is also the first detection of the birth of a supernova.

Supernovae are the explosions of massive stars that are more than 8 times the mass of the Sun, whose cores run out of nuclear fuel and collapse in on themselves to form a neutron star or a black hole. In the process, they launch a powerful shock wave that blows up the star.

Until now, observations of these objects have been of the aftermath, typically several days after the initial explosion, not the first instance of death.

Now, using NASA's orbiting Swift telescope, Carnegie-Princeton University fellows Alicia Soderberg and Edo Berger detected an extremely luminous blast of X-rays released by a explosion of a supernova, dubbed as SN 2008D.

Though they didn't know it, they had just become the first astronomers to have caught a star in the act of exploding.

Astrophysicists have predicted nearly 4 decades ago that the first sign of a supernova would be an X-ray blast, but none had been witnessed before Soderberg's and Berger's Swift observations.

A typical supernova occurs when the core of a vast star runs out of nuclear fuel and collapses under its own gravity to form an ultra-dense object known as a neutron star.

The next activity is what the scientists were able to see for themselves - the newborn neutron star first compresses then rebounds, triggering a shock wave that plows through the star's gaseous outer layers and rips the star apart.

"Using the most powerful radio, optical, and X-ray telescopes on the ground and in space we were able to observe the evolution of the explosion right from the start," said Berger. "This eventually confirmed that the big X-ray blast marked the birth of a supernova," he added.

According to Roger Chevalier, the W.H. Vanderbilt Professor of Astronomy at the University of Virginia, "These are the earliest observations of light from a supernova after the central collapse that initiated the explosion."

"This first instance of catching the X-ray signature of stellar death is going to help us fill in a lot of gaps about the properties of massive stars, the birth of neutron stars and black holes, and the impact of supernovae on their environments," said Neil Gehrels, principal investigator of the Swift satellite.

"We also now know what X-ray pattern to look for. Hopefully we will be able to find many more supernovae at this critical moment," he added.


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