The ball of dust and gas, which is in the process of turning into a Jupiter-like giant, was detected around the star HL Tau by a UK team.

Research leader Dr Jane Greaves said the planet's growth may have been kickstarted when another young star passed the system 1,600 years ago.

Details were presented at the UK National Astronomy Meeting in Belfast.

The scientists studied a disc of gas and rocky particles around HL Tau, which is 520 light-years away and thought to be less than 100,000 years old.

But there is an intriguing suggestion that the gas giant, which is some 14 times the size of Jupiter, could be even younger.