Title: Unpredictable Atmospheric Loss Observed on Exoplanet Orbiting Petulant Red Dwarf Star
Subtitle: Hubble Space Telescope captures unprecedented variability in atmospheric outflow on inhospitable planet AU Mic b
Date: July 27, 2023
Scientists are baffled by the unpredictable atmospheric loss observed on the exoplanet AU Mic b, which orbits the ill-tempered red dwarf star AU Microscopii. The volatile nature of the star, characterized by powerful “super-flares” and blistering ultraviolet radiation, creates an extreme environment that challenges planetary survival and potential habitability.
Located approximately 32 light-years away from Earth, AU Microscopii is only 1% the age of our Sun, making it one of the youngest planetary systems ever observed. The innermost planet, AU Mic b, is about four times the diameter of Earth and orbits just 6 million miles from its fiery and ferocious parent star.
Using the Hubble Space Telescope, astronomers have witnessed the planet’s largely hydrogen atmosphere being stripped off in fits and starts. During a recent observation, hydrogen was detected boiling off to create a large cloud ahead of the planet as it crossed in front of its star. This unexpected variability hints at a more complex and unpredictable interaction between the planet and the red dwarf star than previously imagined.
Keighley Rockcliffe of Dartmouth College in Hanover, New Hampshire, expressed astonishment at the extreme variability observed between orbits. The behavior of the planet’s atmosphere, both when detectable and seemingly non-existent, has presented a stress-test case for scientists’ understanding of planetary evolution.
AU Microscopii’s intense magnetic fields, coupled with its frequent flares and stellar wind, create a hostile environment for planets in close proximity. The prolonged period of high activity on red dwarf stars like AU Microscopii poses a challenge for potential habitability. The flares, which are 100 to 1,000 times more energetic than those emitted by our Sun, can completely strip a planet of its atmosphere.
Scientists are now eager to determine which types of planets can survive such extreme environments and what their ultimate compositions may be. The observations of AU Mic b provide valuable insights into exoplanetary atmospheric escape and evolution, shedding light on the potential habitability of planets orbiting red dwarf stars.
Further observations using the Hubble Space Telescope will continue to unravel the odd variability of AU Mic b and its parent star, allowing researchers to refine their models of exoplanetary atmospheric escape and gain a better understanding of planetary survival in extreme conditions.
The findings by lead author Keighley Rockcliffe and her team have been published in The Astronomical Journal and mark a significant step forward in the study of exoplanets and the potential habitability of distant worlds.
The Hubble Space Telescope, a collaborative project between NASA and ESA, continues to provide groundbreaking observations and expand our knowledge of the cosmos.