Strange 'twin' new worlds found

By Aussiegirl

Curioser and curioser. Our universe continues to astound and amaze. Twin planets orbiting in a dance of mysterious origins. And here we are beholding it all and trying to figure it out.

BBC NEWS | Science/Nature | Strange 'twin' new worlds found

A pair of strange new worlds that blur the boundaries between planets and stars have been discovered beyond our Solar System.
A few dozen such objects have been identified in recent years but this is the first set of "twins".

Dubbed "planemos", they circle each other rather than orbiting a star.

Their existence challenges current theories about the formation of planets and stars, astronomers report in the journal Science.

"This is a truly remarkable pair of twins - each having only about 1% the mass of our Sun," said Ray Jayawardhana of the University of Toronto, co-author of the Science paper.

"Its mere existence is a surprise, and its origin and fate a bit of a mystery."

'Double planet'

The pair belongs to what some astronomers believe is a new class of planet-like objects floating through space; so-called planetary mass objects, or "planemos", which are not bound to stars.

They appear to have been forged from a contracting gas cloud, in a similar way to stars, but are much too cool to be true stars.

And while they have similar masses to many of the giant planets discovered beyond our Solar System (the largest weighs in at 14 times the mass of Jupiter and the other is about seven times more massive), they are not thought to be true planets either.

"We are resisting the temptation to call it a 'double planet' because this pair probably didn't form the way that planets in our Solar System did," said co-researcher Valentin Ivanov of the European Southern Observatory (ESO) in Santiago, Chile.