Hellish new 'Forbidden' planet discovered lurking in distant star system

Pablo Tucker
May 31, 2019

Officially, the worldwide team gave the planet the sobering designation of NGTS-4b, a term derived from the Next-Generation Transit Survey, the ground-based telescope in Chile's Atacama Desert that spotted the exoplanet.

Researchers from Queen's University Belfast were part of the worldwide team that uncovered the existence of NGTS-4b, which has already been given the slightly foreboding nickname of "The Forbidden Planet".

A planet orbiting in a star's habitable zone is regarded as having the best chance of having life.

"Hot Jupiters" and "Super-Earths", which orbit very close to their stars, usually have missing upper atmospheres that have been blown off into space.

To find exoplanets, astronomers use telescopes to watch for a dip in the brightness of a star that indicates a planet passing in front of the view.

It is the first exoplanet of its kind to have been found in the Neptunian Desert, researchers said.


NGTS-4b can complete an entire orbit around its host star in just 1.3 days.

"This planet must be tough-it is right in the zone where we expected Neptune-sized planets could not survive", Richard West, author of the study from the Astronomy and Astrophysics Group at the University of Warwick in the United Kingdom, said in a statement.

The planet was identified by an global team of astronomers using the Next-Generation Transit Survey telescopes (NGTS) at the European Southern Observatory's Paranal facility in the Atacama Desert, Chile.

The planet orbits its star in 1.3 Earth days and is about three times the size of our home planet.

The Neptunian Desert is a region close to stars where large planets with their own atmospheres, similar to Neptune, are not expected to survive, since the strong irradiation from the star would cause any gaseous atmosphere to evaporate, leaving just a rocky core behind.

"For this "Forbidden Planet" to exist at all, there must be something else going on that we haven't quite worked out", Bayliss said.


Richard G. West et al.

It's a common technique known as the transit method to spot new planets.

Richard West, a professor in the department of physics at the University of Warwick who worked on the research, called the discovery "truly remarkable" in a press release. The results are reported in the Monthly Notices of the Royal Astronomical Society. It has a mass of 20.6 Earth masses and a radius 20% smaller than Neptune, which places it well within the so-called 'Neptunian desert'.

Astronomers think that it may only recently, maybe in the last one million years or so, have migrated this close to the star. But the NGTS observatory can pick up dips as small as 0.2 percent.

West added that they are still looking over data to find out whether there are more planets to discover in the Neptunian Desert.


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