Star set to collide with solar system

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Have a good look at this star. For astronomers have discovered that it is on course to collide with the outskirts of our solar system with potentially catastrophic consequences.

New calculations show that the orange dwarf, called Gliese 710, will crash through the Oort Cloud that surrounds the Sun. The disruption to this shell of many billions of icy fragments would launch a shower of comets into the inner solar system, threatening the planets with devastating impacts.

Some believe it could lead to a repeat of the Late Heavy Bombardment that left the Moon covered with craters around 4 billion years ago. The good news is that the star is not expected to arrive for a million or more years.

The threat from Gliese 710, a star with about half the mass of the sun 63 light-years away in the constellation of the Serpent, is rated as 86 per cent likely. That is nearly as good as a certainty.

It comes after a European space telescope called Hipparcos measured precise positions and motions for 1000,000 stars in our cosmic neighbourhood. This allowed astronomers to work out accurately which might come close to the sun as they travel around the galaxy.

Russian astronomer Dr Vadim Bobylev, of the Pulkovo Astronomical Observatory in St Petersburg examined new data from 2007. He identified nine stars that have had or will have particularly close encounters by coming within 3 light-years of us.

But he was startled to find that Gliese 710, which can be seen in small telescopes, has our solar system clearly in its sights. He says it is racing towards us at 30,000mph and on course to crash through the Oort Cloud, which lies around a light-year away, within the next million and a half years.

It could even come within a zone of asteroid-like bodies around Pluto called the Kuiper Belt, though the chances of this are put at only one in a thousand. But some astronomers are suggesting that Gliese 710 might be circled by its own Oort Cloud, which could produce a double shower of hazardous comets.

Dr Bobylev's scientific paper, Searching for Stars Closely Encountering with the Solar System, was submitted to professional journal Astronomy Letters last week. He says: "Our statistical simulations showed that the star has not only a high probability of penetrating into the Oort Cloud, but also a non-zero probability of penetrating into the region where the influence on Kuiper Belt objects is significant."

The new alert comes days after a NASA astrobiology site reported that an invisible brown dwarf star nicknamed Nemesis may be circling the sun and causing mass extinctions of life on Earth every 26 million years. There are hopes that if Nemesis exists, it will be detected by NASA's heat-sensitive Wide-Field Infrared Survey Explorer satellite, WISE, which is currently scanning the sky for brown dwarfs.

http://www.scientificamerican.com/article.cfm?id=star-set-to-collide-with-solar-syst-2010-03

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