Astronomers have detected the biggest flare in the cosmos and ascertained the explosion occurred some 20,000-30,000 light-years away from the earth, which leaves human beings safe.
Dr. Atsushi Miyazaki, a Japanese astronomer who is now working at the Chinese Academy of Sciences (CAS) Shanghai Astronomical Observatory for his post-doctoral research, told Xinhua Wednesday in an interview that "The greatest flare in observation history was so powerful that it made our eyes blur through the telescopes."
"Telecommunications over the earth surface were temporarily affected by the explosion," Miyazaki said.
On Dec. 27 last year, a soft gamma-ray repeater, SGR1806-20, in Sagittarius exploded and emitted a giant flare.
Soft gamma-ray repeaters, remarkable high-energy sources in the Milky Way, are believed to originate from neutron stars with intense magnetic fields. Scientists call SGRs with extremely high magnetic fields magnetars.
In the 0.2-second explosion, total gamma-ray radiation, roughly equaling that from the sun in 250,000 years, emanated from the magnetar.
The Very Large Array in the United States, the Giant Meter-wave Radio Telescope in India, the Australia Telescope Compact Array in Australia and the Nobeyama Millimeter Array in Japan closely tracked the flare. An international collaborative research team published the astronomical finding in the April 28th issue of Nature.
Leading a team at the Nobeyama Millimeter Array for detecting, Dr. Miyazaki obtained a gamma-ray decay profile.
"It was far enough and just like something happened in other people's backyard," he said.
“If it had occurred next door," he said, "the human beings might have faced a lethal threat."
Astronomers suggest that any explosion of such intensity within the range of ten light-years would destroy all life on earth.
The magnetar, with a diameter of 20 kilometers but a mass 1.5 times of the sun, had a magnetic field 1,000 trillion times stronger than that of the earth, which results from its high-speed rotation. It rotated a circle in every 7.5 seconds.
"Too powerful magnetic fields might tear up magnetars and make them explode," said Shen Zhiqiang, a senior researcher at the CAS observatory who closely works with Dr. Miyazaki.
Scientists have already detected three such explosions. The latest one was 100 times larger than the previous two in gamma-rayradiation.
Astronomers found a total of 12 such magnetars in the galaxy, with the nearest one to the earth being 13,000 light-years away from the earth. Every 1,000 years, they estimated, one such magnetar would appear. "The earth is totally safe right now," She said.
"We still cannot predict the explosion of magnetars," Shen said, "But we're confident in calculating how far the explosion is from us."
Some scientists think that the extinction of dinosaurs on the earth might have been caused by similar gamma-ray radiation.
(Xinhua News Agency July 21, 2005)
