A strange exoplanet, NGTS-4b, smaller than Neptune with its own atmosphere has been discovered in the Neptunian Desert, by an international collaboration of astronomers, with the University of Warwick taking a leading role. It is the first exoplanet of its kind to have been found in the Neptunian Desert –the region close to stars where no Neptune-sized planets are found. This area receives strong irradiation from the star, meaning the planets do not retain their gaseous atmosphere as they evaporate leaving just a rocky core.
NGTS — Next-Generation Transit Survey — is situated at the European Southern Observatory’s Paranal Observatory in the heart of the Atacama Desert, Chile. It is a collaboration between UK Universities Warwick, Leicester, Cambridge, and Queen’s University Belfast, together with Observatoire de Genève, DLR Berlin and Universidad de Chile. n the search for planets in other stellar systems, the is part of Paranal’s arsenal of telescopes.
The NGTS is made up of an array of twelve individual telescopes, each with an aperture of 20 centimeters. The array is operated entirely in a robotic mode, which requires no human presence on site. This external operation means the NGTS can continuously monitor the brightness of hundreds of thousands of bright stars in the skies of the southern hemisphere to search for exoplanets.
NGTS-4b, also nick-named ‘The Forbidden Planet’ by researchers, is a planet smaller than Neptune but three times the size of Earth. It has a mass of 20 Earth masses, and a radius 20% smaller than Neptune, and is 1000 degrees Celsius. It orbits around the star in only 1.3 days—the equivalent of Earth’s orbit around the sun of one year.
When looking for new planets astronomers look for a dip in the light of a star—this the planet orbiting it and blocking the light. Usually only dips of 1% and more are picked up by ground-based searches, but the NGTS telescopes can pick up a dip of just 0.2%
Researchers believe the planet may have moved into the Neptunian Desert recently, in the last one million years, or it was very big and the atmosphere is still evaporating.
“This planet must be tough—it is right in the zone where we expected Neptune-sized planets could not survive. It is truly remarkable that we found a transiting planet via a star dimming by less than 0.2% – 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. 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,” said physicist Richard West, with the University of Warwick.
The Daily Galaxy, Max Goldberg via University of Warwick