UNC-CH Physics and Astronomy Master’s Presentation

Amy Glazier

“Evryscope and K2 Constraints on TRAPPIST-1 Superflare Occurrence and Planetary Habitability”

The Evryscopes are the first gigapixel-scale all-sky survey telescopes, designed, constructed, and operated through UNC Chapel Hill⁠. From their locations in Chile and California, the Evryscopes image the entire visible sky every two minutes, enabling the detection of time-varying events such as flares and eclipses for millions of stars across the sky. One of those stars, named TRAPPIST-1, has generated excitement for astronomers, boasting seven small, rocky planets around the same size as Earth—and of which at least three may support liquid water on their surfaces. TRAPPIST-1 is also an active, cool, red star with frequent flaring that could jeopardize its planets’ habitability, as flares of sufficiently high energy can completely destroy ozone in planetary atmospheres and allow potentially sterilizing ultraviolet radiation to bombard planets’ surfaces. However, some prebiotic chemistry requires UV radiation, and stars like TRAPPIST-1 do not emit enough UV flux to sustain these chemical reactions when not flaring, thus raising the possibility of occasional high-energy flares being necessary for enabling prebiotic chemistry⁠ on the planets of the TRAPPIST-1 system. My work combines three years of Evryscope observations of TRAPPIST-1 with Kepler space telescope observations to place the best constraints to date on the star’s high-energy flare rate. I analyze the impact of the star’s high-energy flare rate in the context of biological considerations for the star’s planets, presenting the first assessment of TRAPPIST-1’s impact on both atmospheric destruction and prebiotic chemistry. My results show that TRAPPIST-1’s high-energy flare rate is not high enough to threaten its planets’ atmospheres, but at the same time, its high-energy flare rate is unlikely to provide enough UV flux to facilitate prebiotic chemistry on its planets.