Close Approach

BLOOD STAR of the NEANDERTHALS passed close to our Sun

Small red/brown binary came within 0.8 light years, 70kya
18 Feb 2015 at 08:36, Simon Sharwood

Back when Homo sapiens neanderthalensis strode or shambled or knuckled along the earth, about 70,000 years ago, the prehuman simians may have been able to see a small star passing through the fringes of our solar system.

So say the authors of a new paper, The Closest Known Flyby of a Star to the Solar System, in The Astrophysical Journal Letters.

The star in question is known as Scholz's Star, a binary system comprising a red dwarf and brown dwarf companion first observed in 2013. Boffins have since analysed the star's trajectory and, as the paper explains, concluded that it grazed our Oort cloud.

Lead author Eric Mamajek is associate professor of physics and astronomy at the University of Rochester, which says he became intrigued by the star's unusual path, as it displayed “very slow tangential motion, that is, motion across the sky” but “radial velocity measurements … showed the star moving almost directly away from the solar system at considerable speed.”

That combination's an oddity, so Manajek's co-authors calculated 10,000 possible paths for the star, 98 per cent of which predicted an Ooort encounter.

http://regmedia.co.uk/2015/02/18/scholzs_star.jpgArtist's impression of Scholz's Star. Michael Osadciw/University of Rochester

The star's passage through the Oort is significant because it is widely believed that region of space is filled with objects that may one day dip into our Sun's gravity well to become comets. The paper says Scholz's star probably passed us by about 52,000 Astronomical Units (a single AU measures the distance between Earth and Sol, just a tick under 150 million kilometres) or 0.8 light years. At that distance, any objects the star disturbed are not going to make themselves known for many millennia.

Scholz's star is now about 20 light years away in the constellation Monoceros, and is tricky to spot because it is very dim. But the star is magnetically active and such suns sometimes flare and become much brighter, meaning there's a chance early humans saw something startling as it passed.

Boffins know of no imminent stellar visitor to rival its close encounter, as Manajek and his colleagues also investigated a star called HIP 85605 that has in the past been thought to be a likely visitor some 250,000 years from now. The team's efforts suggest those assumptions were wrong and that HIP 85605 will overshoot us handily. ®