Astronomers find 'planets' in Orion

By BBC News Online science editor Dr David Whitehouse

British astronomers claim to have found 13 "free-floating planets" drifting through a vast cloud of gas and dust in outer space.

The discovery was made during the most sensitive survey ever undertaken of a region in the Orion Nebula where new stars are being born.

Dr Philip Lucas of the University of Hertfordshire and Dr Patrick Roche of the University of Oxford say the objects are not in any orbit and move through space by themselves.

Only two similar such objects have previously been found. The discovery of 13 more in one cluster suggests that very large planets and small stars may be much more common than previously thought.

The research also threw up more than a 100 so-called brown dwarfs. These are objects that are not massive enough to trigger the fusion reactions that make other stars shine. With masses little more than 13 times that of Jupiter, they merely glow with a brownish red light - hence the name.

Giant planets

The new infrared survey of the Trapezium cluster in the Orion Nebula revealed 13 objects below this mass threshold. The smallest has a mass of about eight Jupiters.

It is these objects that the UK astronomers are calling "free-floating planets". They give off only residual heat left over from when they were born.

"These are just clumps of material that coalesce and then slowly fade away," Dr Patrick Roche told the BBC. "They seem to be just floating out there in space. So they are more like failed stars than the planets of our own Solar System which formed out of the debris left over from the creation of the Sun."

Because brown dwarfs and "free-floating planets" quickly cool down, they are easiest to find when they are young and still retain some heat from their birth. The objects in the Trapezium cluster are only about one million years old at most.

The research was undertaken using a new camera on the United Kingdom Infrared Telescope (UKIRT) in Hawaii.

The findings will be published in the Monthly Notices of the Royal Astronomical Society.