Habitable Zones & Global Climate

The Time Evolution Of The Ultraviolet Habitable Zone

By Keith Cowing

Status Report

astro-ph.EP

September 5, 2024

Filed under astro-ph.EP, biochemistry, Biosignatures, Circumstellar Habitable Zone, GJ 163, GJ 229A, GJ 273, GJ 357, GJ 832, Habitable Zone, HD 40307, K2-18, Kepler-62, M-dwarfs, organic chemistry, Proxima Centauri, radiation, space weather, TRAPPIST-1, ultraviolet habitable zone

The Time Evolution Of The Ultraviolet Habitable Zone — Top panels: evolution of CHZ and UVH for Trappist-1, Proxima Centauri, GJ 273, GJ 163, K2-18, GJ 832, GJ 357, GJ 229A, HD 40307 and Kepler-62. In each plot the vertical gray line represents the host star age found in the literature and the relative errors (the gray shaded region around the gray line). Yellow, orange and dark orange lines represent the ages at which fraction of systems with at least one rocky planet without a primordial envelope in the CHZ is equal to 20%, 30%, 40% for each system (according to NGPPS model). The dashed line represents the time where each star settled onto the main sequence. Bottom panels: evolution of the fraction of the radial extension of the CHZ that is overlapping the radial extension of the UVZ for three different values of the NUV atmospheric transmission. — astro-ph.EP

For stars hosting Circumstellar Habitable Zone (CHZ) exoplanets, we investigate the time-evolution of their ultraviolet habitable zone (UHZ), the annular region around a star where an exoplanet could experience a suitable ultraviolet environment for the presence and emergence of life, and the possible intersection of the UHZ with the CHZ.

To estimate their UV luminosity evolution, and therefore the evolution of their UHZ, we analyse Swift-UV/Optical telescope observations and adopt the near-UV luminosity evolutionary tracks derived using GALEX observations of young moving groups. We find that an intersection between CHZ and UHZ could exist (or have existed) around all stars of our sample at different epochs, except for the coldest M-dwarfs (temperature < 2800 K, e.g. Trappist-1).

For hotter M-dwarfs the formation of RNA precursors through cyanosulfidic chemistry triggered by near-UV radiation could occur during the first 1-2 Gyrs. The radial-extension and time-duration of the CHZ-UHZ intersection increase with the stellar effective temperature and the exoplanet atmospheric transmissivity at near-UV wavelengths.

Within our sample, Proxima Centauri represents a golden target for the quest of life outside the Solar system because it experienced a long-lasting and more extended, compared to similar M-dwarfs, CHZ-UHZ intersection.

R. Spinelli, F. Borsa, G. Ghirlanda, G. Ghisellini, F. Haardt, F. Rigamonti

Comments: published in MNRAS Letters, 7 pages, 4 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2409.01401 [astro-ph.EP] (or arXiv:2409.01401v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.01401
Focus to learn more
Related DOI:
https://doi.org/10.1093/mnrasl/slae064
Focus to learn more
Submission history
From: Riccardo Spinelli
[v1] Mon, 2 Sep 2024 18:00:00 UTC (2,231 KB)
https://arxiv.org/abs/2409.01401

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

Follow on Twitter