Climate Regimes Across the Habitable Zone: a Comparison of Synchronous Rocky M- and K-dwarf Planets
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arXiv
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| author | Lobo, Ana H Shields, Aomawa L. |
| author_facet | Lobo, Ana H Shields, Aomawa L. |
| contents | M- and K-dwarf stars make up 86% of the stellar population and host many promising astronomical targets for detecting habitable climates in the near future. Of the two, M dwarfs currently offer greater observational advantages and are home to many of the most exciting observational discoveries in the last decade. But K dwarfs could offer even better prospects for detecting habitability by combining the advantage of a relatively dim stellar flux with a more stable stellar environment. Here we explore the climate regimes that are possible on Earth-like synchronous planets in M- and K-dwarf systems, and how they vary across the habitable zone. We focus on surface temperature patterns, water availability, and implications for habitability. We find that the risk of nightside cold-trapping decreases with increased orbital radius and is overall lower for K-dwarf planets. With reduced atmospheric shortwave absorption, K-dwarf planets have higher dayside precipitation rates and less day-to-night moisture transport, resulting in lower nightside snow rates. These results imply a higher likelihood of detecting a planet with a moist dayside climate in a habitable "eyeball" climate regime orbiting a K-dwarf star. We also show that "terminator habitability" can occur for both M- and K-dwarf land planets, but would likely be more prevalent in M-dwarf systems. Planets in a terminator habitability regime tend to have slightly lower fractional habitability, but offer alternative advantages including instellation rates more comparable to Earth in regions that have temperatures amenable to life. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2408_05951 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Climate Regimes Across the Habitable Zone: a Comparison of Synchronous Rocky M- and K-dwarf Planets Lobo, Ana H Shields, Aomawa L. Earth and Planetary Astrophysics M- and K-dwarf stars make up 86% of the stellar population and host many promising astronomical targets for detecting habitable climates in the near future. Of the two, M dwarfs currently offer greater observational advantages and are home to many of the most exciting observational discoveries in the last decade. But K dwarfs could offer even better prospects for detecting habitability by combining the advantage of a relatively dim stellar flux with a more stable stellar environment. Here we explore the climate regimes that are possible on Earth-like synchronous planets in M- and K-dwarf systems, and how they vary across the habitable zone. We focus on surface temperature patterns, water availability, and implications for habitability. We find that the risk of nightside cold-trapping decreases with increased orbital radius and is overall lower for K-dwarf planets. With reduced atmospheric shortwave absorption, K-dwarf planets have higher dayside precipitation rates and less day-to-night moisture transport, resulting in lower nightside snow rates. These results imply a higher likelihood of detecting a planet with a moist dayside climate in a habitable "eyeball" climate regime orbiting a K-dwarf star. We also show that "terminator habitability" can occur for both M- and K-dwarf land planets, but would likely be more prevalent in M-dwarf systems. Planets in a terminator habitability regime tend to have slightly lower fractional habitability, but offer alternative advantages including instellation rates more comparable to Earth in regions that have temperatures amenable to life. |
| title | Climate Regimes Across the Habitable Zone: a Comparison of Synchronous Rocky M- and K-dwarf Planets |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2408.05951 |