IN­TER­STEL­LAR AS­TER­OID CAP­TURED EN­TER­ING THE SO­LAR SYS­TEM

BBC Earth (Asia) - - Update -

An oddly shaped as­ter­oid has en­tered the So­lar Sys­tem, and is the first con­firmed ob­ject from an­other star. Of­fi­cially dubbed 1I/2017 U1, but known as `Ou­mua­mua (`Ou­mua­mua comes from the Hawai­ian word for ‘scout’), the space rock was cap­tured by the Pan-STARRS 1 tele­scope in Hawaii. First thought to be a comet thanks to its tra­jec­tory and high speed, `Ou­mua­mua had al­ready passed its clos­est to the Sun when it was de­tected, so the race was on to gather as much data as pos­si­ble. At New Year, the as­ter­oid was roughly three times the dis­tance of the Earth from the Sun and is cur­rently speed­ing away from our planet at 90,000km/h.

Te­le­scopes can’t get a good pic­ture of `Ou­mua­mua, but as­tronomers man­aged to de­ter­mine its shape from vari­a­tions in the bright­ness read­ings as the as­ter­oid spins once ev­ery 7.3 hours.

“This un­usu­ally large vari­a­tion in bright­ness means that the ob­ject is highly elon­gated: about 10 times as long as it is wide, with a com­plex, con­vo­luted shape,” said re­searcher Karen Meech. “We also found that it has a dark red colour, sim­i­lar to ob­jects in the outer So­lar Sys­tem, and con­firmed that it is com­pletely in­ert, with­out the faintest hint of dust around it.”

`Ou­mua­mua ap­pears to have come from the di­rec­tion of Vega, a bright star about 25 lightyears away. It’s es­ti­mated that such visi­tors ar­rive roughly once ev­ery year.

“We are con­tin­u­ing to ob­serve this unique ob­ject,” said re­searcher Olivier Hain­aut, “We hope to more ac­cu­rately pin down where it came from and where it is go­ing next on its tour of the Galaxy. And now that we have found the first in­ter­stel­lar rock, we are get­ting ready for the next ones!”

IN­SET: `Ou­mua­mua (marked by blue cir­cle) pho­tographed through te­le­scopes

MAIN IM­AGE: Artist’s im­pres­sion of the elon­gated as­ter­oid named `Ou­mua­mua

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