An Orange Dwarf Star is hurtling Towards us

A star is hurtling towards us. It will almost certainly clip the outskirts of the solar system and send comets towards Earth – though not for a while.

Vadim Bobylev of the Pulkovo Observatory in St Petersburg, Russia, modelled the paths of neighbouring stars using data from the European Space Agency's Hipparcos satellite and from ground-based measurements of the speeds of stars.

He found four previously unidentified stars that will pass within roughly 9.5 light years of Earth. They will tug on the Oort cloud, a diffuse cloud of icy objects around the solar system thought to be a reservoir of comets.

Orange danger
However, the biggest threat comes from another star, Gliese 710, an orange dwarf now some 63 light years away but zooming our way at 14 kilometres per second. Previous studies have suggested that Gliese 710 could pass through the Oort cloud in about 1.5million years.

Bobylev's calculations suggest Gliese 710 has an 86 per cent chance of passing through the Oort cloud. This could scatter millions of comets into paths that cross Earth's orbit. Fortunately, previous work on the effect of a star tangling with the Oort cloud hints the comets would arrive in a trickle, with only one entering an Earth-crossing orbit per year.

Neptune tweak
Gliese 710 also has a 1 in 10,000 probability of coming within 1000 astronomical units – 1 AU being the distance from the Earth to the sun. Such a path could jostle objects in the Oort cloud, the Kuiper belt – a swarm of icy objects beyond Neptune's orbit – as well as others that orbit in a disc between the two regions.

The star could also change Neptune's orbit a fraction, says Paul Weissman of NASA's Jet Propulsion Laboratory in Pasadena, California. "It would be a very significant event."

Although an encounter with Gliese 710 was already thought possible, "it's nice to see it confirmed with a better model and better data", says Weissman. "It's a solid piece of work."

Journal reference: Astronomy Letters, vol 36, p 230