Washington, Aug 13 (ANI): For the first time, astronomers using NASA's Fermi Gamma-ray Space Telescope have detected gamma-rays from a nova- a finding that stunned observers and theorists alike.
The discovery overturns the notion that nova explosions lack the power to emit such high-energy radiation.
A nova is a sudden, short-lived brightening of an otherwise inconspicuous star. The outburst occurs when a white dwarf in a binary system erupts in an enormous thermonuclear explosion.
"In human terms, this was an immensely powerful eruption, equivalent to about 1,000 times the energy emitted by the Sun every year. But compared to other cosmic events Fermi sees, it was quite modest. We're amazed that Fermi detected it so strongly," said Elizabeth Hays, a Fermi deputy project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.
Gamma rays are the most energetic form of light, and Fermi's Large Area Telescope (LAT) detected the nova for 15 days.
Scientists believe the emission arose as a million-mile-per-hour shock wave raced from the site of the explosion.
The story opened in Japan during the predawn hours of March 11, when amateur astronomers Koichi Nishiyama and Fujio Kabashima in Miyaki-cho, Saga Prefecture, imaged a dramatic change in the brightness of a star in the constellation Cygnus.
They realized that the star, known as V407 Cyg, was 10 times brighter than in an image they had taken three days earlier.
The team relayed the nova discovery to Hiroyuki Maehara at Kyoto University, who notified astronomers around the world for follow-up observations.
Before this notice became widely available, the outburst was independently reported by three other Japanese amateurs.
V407 Cyg lies 9,000 light-years away.
The system is a so-called symbiotic binary containing a compact white dwarf and a red giant star about 500 times the size of the Sun.
"The red giant is so swollen that its outermost atmosphere is just leaking away into space," said Adam Hill at Joseph Fourier University in Grenoble, France.
The phenomenon is similar to the solar wind produced by the Sun, but the flow is much stronger.
"Each decade, the red giant sheds enough hydrogen gas to equal the mass of Earth," he added.
A paper detailing the discovery will appear in the latest edition of the journal Science. (ANI)