Artist's impression of planet NGTS-1b with its neighbouring sun University of Warwick/Mark Garlick

A giant planet has been discovered next to small star in a finding which could challenge accepted theories of planet formation.

The existence of such a planet, which is the largest in comparison to its companion star ever discovered, was thought to be extremely unlikely.

NGTS-1b – is a gas giant, about the size of Jupiter - which lies 600 hundred light years away from Earth and orbits a small star with a radius and mass around half that of our sun.

The research identifying the planet, published in the Monthly Notices of the Royal Astronomical Society, was led by Daniel Bayliss and Professor Wheatley from the University of Warwick's Astronomy and Astrophysics Group.

The existence of the planet challenges theories of planet formation which suggest that a planet of this size could not be formed by such a small star. These theories state that, stars of this size can easily form rocky planets but do not gather enough material to form Jupiter-sized planets.

NGTS-1b is a so-called 'Hot Jupiter' – a class of giant exoplanets that are physically similar to Jupiter but with very short orbital periods. NGTS orbits its star every 2.6 days at just 3% of the distance between the Earth and the Sun. The temperature on the surface of the planet is around 530°C.

"The discovery of NGTS-1b was a complete surprise to us - such massive planets were not thought to exist around such small stars," said Bayliss. "This is the first exoplanet we have found with our new NGTS facility and we are already challenging the received wisdom of how planets form."

"Our challenge is to now find out how common these types of planets are in the galaxy, and with the new NGTS facility we are well-placed to do just that."

The planet was identified using the state-of-the-art Next Generation Transit Survey (NGTS) – an observation facility located on the outskirts of the Atacama Desert in northern Chile.

It orbits a red-dwarf – a small class of star that is the most common type in the universe.

"NGTS-1b was difficult to find, despite being a monster of a planet, because its parent star is small and faint," Wheatley said. Small stars are actually the most common in the universe, so it is possible that there are many of these giant planets waiting to found."

"Having worked for almost a decade to develop the NGTS telescope array, it is thrilling to see it picking out new and unexpected types of planets. I'm looking forward to seeing what other kinds of exciting new planets we can turn up," he said.