Hot Super-Earths: Astronomers Identify New Class of Exoplanet

Extrasolar planets with gaseous atmospheres that lie very close to their parent stars are bombarded by a torrent of high-energy radiation, according to the team led by Dr. Mia Lundkvist of Aarhus University, Denmark.

“Due to their proximity to the star, the heat that the exoplanets suffer means that their ‘envelopes’ have been blown away by intense radiation,” the scientists said.

“This violent stripping occurs in exoplanets that are made up of a rocky core with a gaseous outer layer.”

The team used asteroseismology to characterize 102 planetary systems (stars and their planets) to levels of accuracy not achieved before.

“Asteroseismology studies the stellar pulsations, and it allows us to determine the properties of many exoplanet host stars to high accuracy, which in turn markedly improves the planetary properties,” Dr. Lundkvist and her colleagues explained.

“NASA’s Kepler mission has provided high-quality data for thousands of potential exoplanets and their host stars.”

“We exploit these data, using asteroseismology, to make a robust detection of the hot-super-Earth desert, a region in the radius-flux diagram completely void of exoplanets. The detection of the existence of a hot-super-Earth desert confirms that photoevaporation does play a role in shaping the exoplanet population that we see today.”

The results, published in the journal Nature Communications, have important implications for understanding how stellar systems, like our own Solar System, and their planets, evolve over time and the crucial role played by the host star.

“For these planets it is like standing next to a hairdryer turned up to its hottest setting,” said co-author Dr. Guy Davies, from the University of Birmingham, UK.

“There has been much theoretical speculation that such planets might be stripped of their atmospheres.”

“We now have the observational evidence to confirm this, which removes any lingering doubts over the theory.”

“Our results show that planets of a certain size that lie close to their stars are likely to have been much larger at the beginning of their lives,” Dr. Davies said. “Those planets will have looked very different.”