A New Definition of Exoplanet Habitability: Introducing the Photosynthetic Habitable Zone
arXiv:2301.13836 · doi:10.3847/2041-8213/acccfb
Abstract
It may be possible to detect biosignatures of photosynthesis in an exoplanet's atmosphere. However, such a detection would likely require a dedicated study, occupying a large amount of telescope time. It is therefore prudent, while searching for signs of life that we may recognise, to pick the best target possible. In this work, we present a new region, the ``photosynthetic habitable zone'' \textemdash the distance from a star where both liquid water and oxygenic photosynthesis can occur. It is therefore the region where detectable biosignatures of oxygenic photosynthesis are most likely to occur. Our analysis indicates that in the most ideal conditions for life and no atmospheric effects, the photosynthetic habitable zone is almost as broad as the habitable zone. On the other hand, if conditions for life are anything less than excellent and atmospheric effects are even moderate, the photosynthetic habitable zone is concentrated at larger separations around more massive stars. Such cases are also not tidally locked to their host star, which could result in planetary rotation periods similar to the Earth's. We identify five planets, Kepler-452 b, Kepler-1638 b, Kepler-1544 b and Kepler-62 e and Kepler-62 f, that are consistently in the photosynthetic habitable zone for a variety of conditions, and we predict their day lengths to be between 9 and 11 hours. We conclude that the parameter space in which we should search for signs of life is much narrower than the standard habitable zone.
12 pages, 3 figures, accepted to ApJL
References in corpus (18)
- Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
- New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
- Vegetation's Red Edge: A Possible Spectroscopic Biosignature of Extraterrestrial Plants
- Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
- How to Characterize Habitable Worlds and Signs of Life
- Ranges of Atmospheric Mass and Composition of Super Earth Exoplanets
- Disequilibrium biosignatures over Earth history and implications for detecting exoplanet life
- The Role of N2 as a Geo-Biosignature for the Detection and Characterization of Earth-like Habitats
- Evidence for the volatile-rich composition of a 1.5- planet
- TOI-1452 b: SPIRou and TESS reveal a super-Earth in a temperate orbit transiting an M4 dwarf
- Sensitive Probing of Exoplanetary Oxygen via Mid Infrared Collisional Absorption
- Differentiating Modern and Prebiotic Earth Scenarios for TRAPPIST-1e: High-resolution Transmission Spectra and Predictions for JWST
- Detecting the proposed CH4-CO2 biosignature pair with the James Webb Space Telescope: TRAPPIST-1e and the effect of cloud/haze
- Terminator Habitability: the Case for Limited Water Availability on M-dwarf Planets
- The TRAPPIST-1 JWST Community Initiative
- Potential long-term habitable conditions on planets with primordial H-He atmospheres
- The Effect of Land Fraction and Host Star Spectral Energy Distribution on the Planetary Albedo of Terrestrial Worlds
- Characteristics of aquatic biospheres on temperate planets around Sun-like stars and M-dwarfs