Exoplanets can be made less habitable by stars' flares

In this new study, NYUAD Center for Space Science Research Scientist Dimitra Atri found that not all exoplanets in habitable zones will be able to maintain hospitable conditions for life. Exoplanets in close proximity to stars are subject to radiation bursts which can disrupt habitable conditions unless the exoplanet has significant atmospheric or magnetic shielding.

In the study, published in the journalMonthly Notices of the Royal Astronomical Society: Letters, Atri explores how flares from stars affect a planet's surface radiation dose, and if that can disrupt the planet's ability to host life. The role of a planet's magnetic field strength and its atmosphere in providing shielding from these bursts was also examined. The factors measured include flare strength and spectrum, as well as the planetary atmospheric density and magnetic field strength. To calculate the surface radiation dose, particle spectra from 70 major flare emitting events (observed between 1956 and 2012) were used as proxy, and the GEANT4 Monte Carlo model was used to simulate flare interaction with exoplanetary atmospheres.

From this study it was concluded that flares can abruptly increase the radiation level on planetary surfaces and have the capability to disrupt potentially habitable conditions on planets. It was also found that the atmospheric depth (column density) and planetary magnetic field are major factors in protecting planets from flares and maintaining a substantial planetary atmosphere.

"As we continue to explore the planets of the solar system and beyond, discovering if these planets have the ability to support life continues to be of immense importance," said Atri. "More progress in this area will improve our understanding of the relationship between extreme solar events, radiation dose, and planetary habitability."