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.
‘Amazing diversity‘
The
two objects have similar spectra and colours, suggesting that they
formed at the same time about a million years ago.They are separated by
about six times the distance between the Sun and Pluto, and can be
found in the Ophiuchus star-forming region some 400 light years away.
They go under the official name Oph 162225-240515, or Oph 1622 for
short.”Recent discoveries have revealed an amazing diversity of worlds
out there,” said Dr Jayawardhana. “Still, the Oph 1622 pair stands out
as one of the most intriguing, if not peculiar.”His colleague, Dr
Ivanov, said they were curious to find out whether such pairs are
common or rare.”The answer could shed light on how free-floating
planetary-mass objects form,” he added.Oph 1622 was discovered using
the ESO’s New Technology Telescope at La Silla, Chile. Follow-up
studies were conducted with the ESO’s Very Large Telescope.