Researchers say the giant planet, named BD+20 1790b, is 35 million years old and six times the mass of Jupiter. It is situated 83 light years away from Earth and is the youngest planet orbiting a star of a similar size to the sun, the astronomers said. Only one young planet, aged 100 million years, was previously known but the newly-discovered planet is about three times younger, said the research published in the Astronomy & Astrophysics journal.

Dr Maria-Cruz Gálvez-Ortiz, a University of Hertfordshire astronomer, described it as ''an exciting discovery''. ''There are still very few extrasolar planets that have been discovered – only about 420," said Dr Gálvez-Ortiz, who was among the international team which identified the planet.

Young stars are usually excluded from planet searches because they have intense magnetic fields that generate a range of phenomena known collectively as stellar activity, including flares and spots. This can make it difficult to disentangle the signals of planets and activity.

''Overcoming the interference caused by the activity was a major challenge for the team, but with enough data from an array of large telescopes the planet's signature was revealed," Dr Gálvez-Ortiz said. Knowledge about early stages of planet evolution is relatively limited, the university said.

It is hoped the detection of young planets will help scientists investigate the early stages of planetary evolution. BD+20 1790b was discovered using observations made with different telescopes over the past five years. The team included astronomers from Spain and the US.