"This planet must be tough - it is right in the zone where we expected Neptune-sized planets could not survive,"said Richard West in a statement, study author and principal research fellow from the University of Warwick's department of physics".
The telescopes monitor the characteristic dip in a star's brightness that signals an exoplanet is nearby: the planet blocks out the light from the star as it passes along its orbit. That's rather shocking, especially when you consider that it's so close to its star that it completes an entire orbit in less than two Earth days. However NGTS-4b still has its atmosphere of gas.
An global team led by astronomers with the University of Warwick in the United Kingdom issued an announcement this week that sounds like a summary for a Star Trek episode: "The "Forbidden" Planet has been found in the 'Neptunian Desert'".
Researchers have found a "forbidden" planet roughly three times the size of Earth in an area known as the Neptunian Desert, a place where it should not exist. It's a common technique known as the transit method to spot new planets.
However, the discovery of the "Forbidden" planet has left scientists baffled.
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.
Discovered using the state-of-the-art Next-Generation Transit Survey (NGTS) observing facility, created to search for transiting planets on bright stars, but NGTS-4b is so small other ground surveys wouldn't have spotted it. The NGTS telescopes can pick up a dip of 0.2 percent, unlike other ground-based searches that can only pick up dips of one percent or more. Planets orbiting so close to a star usually have no atmosphere, because it boils off due to radiation and heat.
The researchers suspect that NGTS-4b may have only recently moved into the Neptunian Desert, perhaps over the last million years.
In the case of NGTS-4b, however, the astronomers' telescopes were able to detect the planet even though it only dimmed the star's light by less than 0.2 per cent. The results are reported in the Monthly Notices of the Royal Astronomical Society.
"We are now scouring our data to see if we can see any more planets in the Neptune Desert". It is dense and hot, with a mass 20 times that of Earth and an average surface temperature of 1000 degrees Celsius.