An international team of scientists has discovered evidence of a series of massive supernova explosions near our solar system, which showered the Earth with radioactive debris.
The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans.
The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU).
“We were very surprised that there was debris clearly spread across 1.5 million years,” said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering. “It suggests there were a series of supernovae, one after another.
The team from Australia, the University of Vienna in Austria, Hebrew University in Israel, Shimizu Corporation and University of Tokyo, Nihon University and University of Tsukuba in Japan, Senckenberg Collections of Natural History Dresden and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, also found evidence of iron-60 from an older supernova around eight million years ago, coinciding with global faunal changes in the late Miocene.
A supernova is a massive explosion of a star as it runs out of fuel and collapses.
The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon.
Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.
The supernova explosions create many heavy elements and radioactive isotopes which are strewn into the cosmic neighbourhood.Follow @gorkhapost
2 Nepalis in Lhasa jail for smuggling gold
RASUWA — Two Nepali youths are reported to be in a jail in Lhasa of China, on the charge of their involvement in gold smuggling.
Gyal Dorje Tamang of Gosaikunda Rural Municipality-5 in Rasuwa and Bikash Waiba of Hakubesi of Aamachhodongmo Rural Municipality were detained in Chinese territory by the customs department informers of the Tibet government around a month ago as they were about to enter Nepal on a truck bearing the Nepali number plate.
The Chinese side confiscated nine pieces of precious yellow metal from the two, Rasuwa District Police Office quoted the Nepal Consulate General Office in Lhasa as saying.
According to Rasuwa DPO’s Inspector of Police Dhruba Silwal, further details regarding the case are awaited.
It may be noted that the Chinese side has already started implementing the proposal floated by the Nepali side during the past border-security meetings to increase its surveillance in such illegal affairs bearing in mind increasing smuggling of gold into Nepali territory via China, as Silwal said.Follow @gorkhapost