The First Naked-Eye Superflare Detected from Proxima Centauri
Proxima b is a terrestrial-mass planet in the habitable-zone of Proxima Centauri. Proxima Centauri’s high stellar activity however casts doubt on the habitability of Proxima b.
Sufficiently bright and frequent flares and any associated proton events may destroy the planet’s ozone layer, allowing lethal levels of UV flux to reach its surface. In March 2016, the Evryscope observed the first naked-eye-visible superflare detected from Proxima Centauri. Proxima increased in brightness by a factor of ~68 during the superflare and released a bolometric energy of 10^33.5 erg, ~10X larger than any previously-detected flare from Proxima. Over the last two years the Evryscope has recorded 23 other large Proxima flares ranging in bolometric energy from 10^30.6 erg to 10^32.4 erg; coupling those rates with the single superflare detection, we predict at least five superflares occur each year.
Simultaneous high-resolution HARPS spectroscopy during the Evryscope superflare constrains the superflare’s UV spectrum and any associated coronal mass ejections. We use these results and the Evryscope flare rates to model the photochemical effects of NOx atmospheric species generated by particle events from this extreme stellar activity, and show that the repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years.
We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100X the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares.
Ward S. Howard, Matt A. Tilley, Hank Corbett, Allison Youngblood, R. O. Parke Loyd, Jeffrey K. Ratzloff, Octavi Fors, Daniel del Ser, Evgenya L. Shkolnik, Carl Ziegler, Erin E. Goeke, Aaron D. Pietraallo, Joshua Haislip, Nicholas M. Law
(Submitted on 5 Apr 2018)
Comments: 7 pages, 5 figures, submitted to AAS Journals
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1804.02001 [astro-ph.EP] (or arXiv:1804.02001v1 [astro-ph.EP] for this version)
Submission history
From: Ward Howard
[v1] Thu, 5 Apr 2018 18:00:18 GMT (1506kb,D)
https://arxiv.org/abs/1804.02001
Astrobiology
