Astronomers Find Rogue ‘Forbidden’ Planet In A Place Where It Shouldn’t Exist

NASA / JPL-CaltechWikimedia Commons / Cropped and Resized

A massive planet three times the size of Earth has been discovered in the unlikeliest of places. Nicknamed the “Forbidden” planet, the object has been detected in an area around its parent star where no planets of its size should exist.

According to, this intriguing exoplanet – a term used for planets that exist outside the boundaries of our own solar system – has 20 times the mass of Earth and a radius that’s 20 percent smaller than that of the gas giant Neptune. As such, it has been classified as a sub-Neptune – an exoplanet that’s smaller than Neptune, but still boasts two to three times the radius of Earth, as previously reported by The Inquisitr.

While astronomers have stumbled upon quite a few sub-Neptunes in the past, this particular exoplanet is a very special case. For one thing, it has been found in the so-called “Neptunian Desert” – the area around a star that’s too close and vulnerable to radiation for Neptune-sized planets to exist.

This particular region is so close to the star that it gets heavily irradiated – so much so that any Neptune-sized forming in this area would not be able to hold on to their atmospheres and would gradually evaporate. However, the newfound exoplanet has not only managed to survive the hostile environment, but it has even retained a gaseous atmosphere.

“This planet must be tough – it is right in the zone where we expected Neptune-sized planets could not survive,” said Dr. Richard West, a physicist at the University of Warwick in the U.K. and lead author of a study announcing the incredible discovery.

Another thing that makes this rogue exoplanet really stand out is the way it was discovered. The object was spotted with the help of the Next-Generation Transit Survey (NGTS), a wide-field photometric survey located at the European Southern Observatory’s Paranal Observatory in Chile. Since the NGTS played a crucial part in uncovering its whereabouts, the rogue exoplanet has been named NGTS-4b.

The NGTS was specifically designed to pick up Neptune-sized and smaller exoplanets that orbit bright stars. Also known as the transit method, the technique analyzes the brightness of a star in an effort to catch any dips that could be caused by potential planets passing in front of (transiting) the star and, thus, temporarily blocking out its light.

Under normal circumstances, ground-based observatories usually detect transiting planets that dim their star by more than 1 percent. But the sharp eyes of the NGTS found the new exoplanet after picking up a dimming far below that value, one of less than 0.2 percent.

“This has never been done before by telescopes on the ground, and it was great to find after working on this project for a year,” said West, who described the discovery as “truly remarkable.”

Artist's rendition of the exoplanet K2-288Bb, a sub-Neptune located 226 light-years away and which orbits its star every 31.3 days.Featured image credit: NASA's Goddard Space Flight Center/Francis Reddy

Given its peculiar properties, it’s easy to see why astronomers have dubbed NGTS-4b the “Forbidden” planet. As the University of Warwick points out, NGTS-4b is “the first exoplanet of its kind to have been found in the Neptunian Desert.” The planet whips around its star in just 1.3 days and is hotter than Mercury, boasting a temperature of 1,832 degrees Fahrenheit.

“NGTS-4b represents the shallowest transiting system ever discovered from the ground, and is the smallest planet discovered in a wide-field ground-based photometric survey,” West’s team show in their study, recently published in the Monthly Notices of the Royal Astronomical Society.

The scientists believe that a possible explanation for how NGTS-4b has managed to endure the radiation blasts of the Neptunian Desert is that the planet migrated to the area relatively recently, in the last 1 million years. Another possibility is that the planet was once even bigger than it currently is, and it’s still evaporating under the blaze of its parent star.

“Its survival in the Neptunian Desert may be due to an unusually high-core mass, or it may have avoided the most intense X-ray irradiation by migrating after the initial activity of its host star had subsided,” the authors write in their paper.

Going forward, West hopes to uncover whether more planets could be hiding in the Neptunian Desert of the star.

“Perhaps the desert is greener than was once thought.”