Monster planet discovery offers new insights into planet formation

A giant planet – the existence of which was previously thought extremely unlikely – has been discovered by an international collaboration of astronomers, including researchers from our Department of Physics and Astronomy.

The first planet discovered by the Next-Generation Transit Survey consortium is highly unusual. NGTS-1b is the largest planet compared to the size of its companion star ever discovered in the universe.

NGTS-1b is a gas giant six hundred light years away, the size of Jupiter, and orbits a small star with a radius and mass half that of our sun.

Its existence challenges theories of planet formation which state that a planet of this size could not be formed by such a small star. According to these theories, small stars can readily form rocky planets but do not gather enough material together to form Jupiter-sized planets. The planet is a hot Jupiter, at least as large as the Jupiter in our solar system, but with around 20% less mass. It is very close to its star – just 3% of the distance between Earth and the Sun – and orbits the star every 2.6 days, meaning a year on NGTS-1b lasts two and a half days.

Dr Matt Burleigh, a co-author on the paper and Leicester lead on follow-up studies of the planets found by NGTS, commented: “A huge amount of effort by many people both here at Leicester and at our partner institutions goes into every planet discovery. We are fortunate that NGTS-1b turns out to be so unusual and challenges our current understanding of how planets form.”

The researchers spotted the planet using the state-of-the-art Next-Generation Transit Survey (NGTS) - a wide-field observing facility made of a compact ensemble of telescopes, designed to search for transiting planets on bright stars - run by the Universities of Warwick, Leicester, Cambridge, Queens University Belfast, Observatoire de Genève, DLR Berlin and Universidad de Chile.

The planet orbits a red M-dwarf – the most common type of star in the universe, leading to the possibility that there could be more of these planets waiting to be found by the NGTS survey.

Dr Sarah Casewell, a world leader on cool red stars, the principal targets of the NGTS survey, said: “This is only the third gas giant and the most massive to be discovered around an M dwarf. It is fantastic to see that NGTS is making such ground breaking discoveries so early on in the survey and I am really excited to see what else we will discover.”

Dr Mike Goad, Leicester lead on the calibration of the NGTS cameras and co-author on the paper said: “It is gratifying that the ~two years of effort spent characterizing the performance of the 12 NGTS cameras in our state-of-the-art facilities is starting to pay dividends.”

Dr Richard Alexander, theoretical astrophysicist at Leicester and co-author on the paper, said: "To date most exoplanet surveys have looked at stars like the Sun, but most stars in the Milky Way are much smaller.  Through discoveries like this the NGTS project is opening a new window on the exoplanet population, and will offer key new insights into how planets form and evolve in different environments."

Liam Raynard, a post-graduate student from our Department of Physics and Astronomy working on NGTS discoveries, said: “It is exciting that the first planet discovered by NGTS is so interesting. I look forward to seeing what other discoveries we will make in the near future.”

The research, ‘NGTS-1b: a hot Jupiter transiting an M-dwarf’, is published in the Monthly Notices of the Royal Astronomical Society.