An international team of astronomers has discovered a massive Jupiter-sized planet orbiting an M-dwarf star only half the mass and size of our Sun. The existence of so massive a planet around such a small star challenges current theories regarding planetary formation.

It was previously believed that, whilst M-dwarf stars are capable of gathering the materials needed to produce rocky worlds, they lacked the gravitational clout to draw in enough material to allow for the formation of massive Jovian planets.

The new discovery was made using the Next Generation Transit Survey (NGTS) telescope located at the ESO's Paranal Observatory in Chile. The NGTS is comprised of an array of 12 individual telescopes that continuously observe the sky in an effort to detect transiting exoplanets orbiting distant, bright stellar bodies.

Exoplanets spotted by the NGTS can then be observed in greater detail by more powerful instruments, such as the Hubble Space Telescope, and the future James Webb Space Telescope.

As the NGTS observed the night sky, it detected the tell-tale periodic dip in light from the M-dwarf star created as the previously unknown exoplanet, now designated NGTS-1b, passed between Earth and the diminutive stellar body, blocking some of its light.

Astronomers were then able to determine characteristics of NGTS-1b, including its mass, size and orbit by observing how much the parent star "wobbled" as a result of the planet's gravitational influence.

The results of this analysis suggest that NGTS-1b is a huge gas giant planet roughly the same size of Jupiter, but with 20 percent less mass. The exoplanet orbits incredibly close to its parent star, with only 3 percent the distance between the Earth and our Sun separating the two celestial objects.

The close proximity of NGTS-1b to its parent star has had the effect of super heating the gas giant – giving it a temperature of around 530 °C (800 kelvin).

"The discovery of NGTS-1b was a complete surprise to us – such massive planets were not thought to exist around such small stars. 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," comments Dr. Daniel Bayliss of the University of Warwick's Astronomy and Astrophysics Group, and lead author of the research paper detailing the discovery.

"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 study has been published in the Monthly Notices of the Royal Astronomical Society.

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