‘Forbidden’ planet discovered in Neptunian Desert

Posted June 01, 2019

Astronomers from the University of Warwick and other organizations described a rogue planet that they spotted in the "Neptunian Desert", some 920 light-years away from Earth.

According to calculations, the new exoplanet is smaller than Neptune but three times the size of Earth. It is also possible that the Forbidden Planet may have been a massive world and that its atmosphere of gas is still in the process of evaporating.

"NGTS-4b may have survived in the Neptunian Desert due to an unusually high core mass", the authors suggest, "or it might have migrated to its current close-in orbit after this epoch of maximum stellar activity". But thanks to the excellent telescopes at SAAO in Sutherland, we were able to detect and confirm the transit, convincing ourselves the planet is real.

Researchers hope this is just the beginning for locating planets in the Neptune desert. The area, highly irradiated, is indeed hostile to giant planets who cannot keep their gaseous atmosphere. It also seems to retain an atmosphere, which particularly surprised the researchers, since at such a close distance to its star it would be hard for the planet to cling to gas. Researchers estimate it stokes the planet's atmosphere to a downright infernal 1,832 degrees Fahrenheit or roughly 1,000 Celsius. The reason for a label right out of a sci-fi thriller is that this exoplanet has been found where scientists didn't think one could exist, in what's known as the Neptunian Desert, reports Australia's ABC. With a dip nearly that small, this exoplanet is, by a long way, the shallowest transiting planet ever discovered by a ground-based survey (the transit is less than 0.2%).

NGTS-4b was discovered using the Next-Generation Transit Survey (NGTS) facility, created to search for transiting planets around bright stars. However, NGTS-4b still retains its atmosphere.

Researchers often look for a dip in the light of stars when trying to find new planets beyond the galaxy.

"We are now scouring out data to see if we can see any more planets in the Neptune Desert - perhaps the desert is greener than was once thought", West concluded.

The facility is located at Paranal Observatory in the Atacama desert in northern Chile, about 2 km from ESO's Very Large Telescope and 0.5 km from the VISTA Survey Telescope.

Dr Bayliss and his colleagues suspect the planet may have moved into the "Neptunian Desert" only recently, in the last 1 million years, or it's very big and so its atmosphere is still evaporating.

"It is truly remarkable that we found a transiting planet via a star dimming by less than 0.2 per cent".