Supernovae emit gamma rays, typically in an intense burst coinciding with the visible light emitted during the explosion. The gamma-ray burst (GRB) is not uniform in all directions; there is a direction dependence on gamma-ray intensity, often concentrated in jets. A nearby supernova, approximately 10-20 light years away, poses a risk of damaging the Earth's ozone layer due to radiation exposure. The brightest recorded GRB occurred on December 27, 2004, from SGR 1806-20, located about 50,000 light years from Earth.
PREREQUISITESAstronomers, astrophysicists, environmental scientists, and educators interested in the effects of cosmic events on Earth and the mechanisms behind supernovae and gamma-ray bursts.
There is certainly concern that a nearby SN could do a lot of damage to the Earth. One would have to determine a rad dosage that would damage the ozone layer or irradiate the Earth's surface, then use the source strength to determine the closest safe distance based on 1/r2 reduction in strength.Mike2 said:Thanks. But what I'm really interested in is whether a nearby supernova could damage the ozone layer. The History channel resently had a show that described how a GRB might destroy the ozone layer and all the consequences that followed. Then I remembered a similar show narated by Patric Steward describing the same effects with a nearby supernova. I was just wondering how close a nearby supernova would have to be in order to cause those effects. Does anybody recall the show or know about such things? Thanks.
Scientists have detected a flash of light from across the Galaxy so powerful that it bounced off the Moon and lit up the Earth's upper atmosphere. This "giant flare" was the brightest explosion ever detected from beyond the Solar System. For over a tenth of a second the remarkable flare was actually brighter than a full moon.
NASA and European satellites and ground-based telescopes around the world detected the giant flare on 27 December 2004. Scientists from twenty institutes joined the observations. Two science teams report about this unprecedented event in an issue of Nature.
The light detected from the giant flare was far brighter in gamma rays than visible light or X-rays. It was probably created by an unprecedented eruption on the surface of an exotic neutron star which is classed both as an ultra-magnetic magnetar and as a soft gamma repeater (SGR). The designation of the neutron star that erupted is SGR 1806-20, about 50,000 light years from Earth in the constellation Sagittarius.
The connection between the long Gamma Ray Bursts (GRBs) and Type Ic Supernovae (SNe) has revealed interesting diversity. We review the following types of the GRB-SN connection. (1) GRB-SNe: The three SNe all explode with energies much larger than those of typical SNe, thus being called Hypernovae (HNe). They are massive enough for forming black holes. (2) Non-GRB HNe/SNe: Some HNe are not associated with GRBs. (3) XRF-SN: SN 2006aj associated with X-Ray Flash 060218 is dimmer than GRB-SNe and has very weak oxygen lines. Its progenitor mass is estimated to be small enough to form a neutron star rather than a black hole. (4) Non-SN GRB: Two nearby long GRBs were not associated SNe. Such 'dark HNe' have been predicted in this talk (i.e., just before the discoveries) in order to explain the origin of C-rich (hyper) metal-poor stars. This would be an important confirmation of the Hypernova-First Star connection. We will show our attempt to explain the diversity in a unified manner with the jet-induced explosion model.