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Title: Nasa sees brightest supernova
Source:
http://www.guardian.co.uk
URL Source: http://www.guardian.co.uk/space/article/0,,2074918,00.html
Published: May 8, 2007
Author: James Randerson
Post Date: 2007-05-08 09:19:15 by robin
Keywords: None
Views: 87
Comments: 3
The huge stellar explosion released around 100 times more energy than a typical supernova and was 100 million billion times brighter than the sun at its peak. It is very unusual to observe the death of a super-massive star, so scientists will be keen to use the data from the orbiting telescope and others on the ground to piece together what happened. "We understand rather little about the most massive stars in the universe," said Jane Drew an astrophysicist at Imperial College London "They are very rare so we get our hands on them not very often. It's a bit like always getting to the crime scene after the criminal has gone and getting the catastrophe that is left behind." She said super-massive stars had a "live fast, die young" existence, in astronomical terms. They typically burn for just 1m years, while our sun has been in existence for more than 4.5 bn. "We know that they live short and very furious lives," she said, "They almost switch on and then, bang, they are gone." The star that gave rise to the explosion was around 150 times more massive than our own sun. Usually, supernovae occur when stars exhaust their fuel and collapse. But astonomers think the SN 2006gy supernova was different. Its massive core may have produced so much gamma radiation that some of the energy was converted into particle and anti-particle pairs. This would have produced a massive gravitational pull, tugging the star in on itself and triggering runaway thermonuclear reactions that caused the massive explosion, which spewed detritus into space. Similar acts of massive cosmic littering have been vital for the development of the universe as we know it and, crucially for life. Stars are factories that produce heavier elements, such as iron, so life could not exist without them. "Of all exploding stars ever observed, this was the king," said Alex Filippenko, leader of ground-based observations at the Keck observatory in Mauna Kea, Hawaii, and the Lick observatory at Mount Hamilton, California. "We were astonished to see how bright it got and how long it lasted." "This was a truly monstrous explosion, 100 times more energetic than a typical supernova," said Nathan Smith of the University of California at Berkeley, who led a team. "That means the star that exploded might have been as massive as a star can get - about 150 times [the size of] our sun. We've never seen that before." SN 2006gy will not trouble us too much because the galaxy it is in - called NGC 1260 - is 240m light years away. However, closer to home, in the Milky Way, is a star called Eta Carinae, a mere 7,500 light years or so away. This has been losing mass rapidly and looks like it might go supernova. It is hard to predict what the event would look like to us, but some suggest it would be so bright that it would be visible alongside the sun during the day. "We don't know for sure if Eta Carinae will explode soon, but we had better keep a close eye on it just in case," said Mario Livio of the Space Telescope Science Institute, Baltimore. "Eta Carinae's explosion could be the best star show in the history of modern civilisation." Nasa sees brightest supernova
James Randerson
Tuesday May 8, 2007
Guardian Unlimited
A Nasa illustration shows what the supernova may have looked like. Photograph: AP/Nasa/Chandra x-ray centre/M Weiss
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#1. To: robin (#0)
I thought a supernova in our own galaxy ran the risk of sterilizing the planet. Least I've heard that claimed somewhere.
Apparently, a supernova sends a beam of radiation that is highly directed. If you are in its direct path, it could be bad news. Fortunately, the star most likely to give a supernova would generate a beam pointing away from us, so the most we'd get is some impressive nighttime fireworks.
Scientists were supposing quasars that emit gamma rays did that due to their spin, but I've never heard of that with a nova/supernova. Wiki had this to say: http://en.wikipedia.org/wiki/Supernovas According to that, 7500 light years should be no problem.... so far as were told, anyway.
However, closer to home, in the Milky Way, is a star called Eta Carinae, a mere 7,500 light years or so away. This has been losing mass rapidly and looks like it might go supernova. It is hard to predict what the event would look like to us, but some suggest it would be so bright that it would be visible alongside the sun during the day.
#2. To: Neil McIver (#1)
I thought a supernova in our own galaxy ran the risk of sterilizing the planet. Least I've heard that claimed somewhere
#3. To: Rupert_Pupkin (#2)
A near-Earth supernova is an explosion resulting from the death of a star that occurs close enough to the Earth (roughly fewer than 100 light-years away) to have noticeable effects on its biosphere. Gamma rays are responsible for most of the adverse effects a supernova can have on a living terrestrial planet. In Earth's case, gamma rays induce a chemical reaction in the upper atmosphere, converting molecular nitrogen into nitrogen oxides, depleting the ozone layer enough to expose the surface to harmful solar and cosmic radiation. The gamma ray burst from a nearby supernova explosion has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth.[66]
Speculation as to the effects of a nearby supernova on Earth often focuses on large stars as Type II supernova candidates. Several prominent stars within a few light centuries from the Sun are candidates for becoming supernovae in as little as a millennium, such as Betelgeuse, a red supergiant 427 light-years from Earth.[67] Though spectacular, these "predictable" supernovae are thought to have little potential to affect Earth.
Recent estimates predict that a Type II supernova would have to be closer than eight parsecs (26 light-years) to destroy half of the Earth's ozone layer.[68] Such estimates are mostly concerned with atmospheric modeling and considered only the known radiation flux from SN 1987A, a Type II supernova in the Large Magellanic Cloud. Estimates of the rate of supernova occurrence within 10 parsecs of the Earth vary from once every 100 million years[69] to once every one to ten billion years.[70]
Type Ia supernovae are thought to be potentially the most dangerous if they occur close enough to the Earth. Because Type Ia supernovae arise from dim, common white dwarf stars, it is likely that a supernova that could affect the Earth will occur unpredictably and take place in a star system that is not well studied. One theory suggests that a Type Ia supernova would have to be closer than a thousand parsecs (3300 light-years) to affect the Earth.[71] The closest known candidate is IK Pegasi (see below).[72]
In 1996, astronomers at the University of Illinois at Urbana-Champaign theorized that traces of past supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata. Subsequently, iron-60 enrichment has been reported in deep-sea rock of the Pacific Ocean by researchers from the Technical University of Munich.[73][74][75]
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