Kepler-737b is an exoplanet with 1.96 R🜨 (0.175 RJ). Its mass is unknown, but is estimated at 4.5 ME based on a mass-radius relationship.[1][3][4] If the 4.5-earth mass estimate is correct, this gives the planet an approximate density of 3.3 times that of water, giving it the possibility of being a mini-Neptune or, more favorable to habitability, a water world. Due to its stellar flux 121% that of Venus, it may be a smaller version of GJ 1214b, a classic superpressured water world. The planet's equilibrium temperature is 298 K (25 °C).
Star
The star's designations include Kepler-737 and KOI-947.[2] It is an earlyM-star. The mass is 0.51 solar masses and its radius is 0.48 times that of the Sun.[2][5] The temperature of the star is 3813 K and its metallicity is -0.24, significantly lower than the Sun's.[2] The host star's age is 3.89 billion years, 680 million years younger than the Sun.[6]
Orbit
Kepler-737b orbits its star once every 28.5992 days.[2] It may be within the inner part of the habitable zone, depending on the habitable zone model used. The conservative model/models place it over 1 Earth flux level outside of the habitable zone, but some very optimistic models place it inside the far inner section of the extended habitable zone. If it is not a mini-Neptune, then it might have a small chance of being habitable. It would be substantially hotter than Earth, due to its stellar flux 2.297 times that of Earth,[3] greater than that of Venus,[7] and resulting equilibrium temperature of 298 K (25 °C; 77 °F).[1]
Discovery
Kepler-737b is a confirmed exoplanet that was found by Kepler using the transit method.[2] It was confirmed on May 10,[2] 2016.[1]
With a stellar flux 2.297 times that of Earth,[3] greater than that of Venus,[7] Kepler-737b is unlikely to be habitable. However, Kepler-737b is considered to be in the habitable zone by the Open Exoplanet Catalogue,[2] based on an extremely optimistic habitable zone model that also places Venus in the habitable zone.[9] Due to its equilibrium temp. of 298 K, with and earth-like GE it would be about sixty degrees Celsius, and with twice its GE, ninety degrees. It is likely tidally locked due to its short orbit; a tidally locked planet would have one side facing the star permanently while the other would be in constant darkness.[10] If Kepler-737b has little or no atmosphere, this could make one side too hot to live on, and the other too cold. However, there may be a "sweet spot" in between the two, where liquid water can exist. This spot would be the planet's terminator line. Kepler-737b may instead have atmospheric circulation that would distribute the heat around the planet, potentially making a large portion of it habitable,[11] although given its stellar flux the most likely scenario is that the planet's surface is too hot to be habitable. Water on Kepler-737b's surface could also distribute heat.[12]
Kepler-737b's density is unknown, so it could either be a rocky super-Earth or a mini-Neptune. The fact that the planet is quite likely to have no magnetic field[citation needed] could spark adaptations to the relatively high radiation level, such as a thick shell of a substance that could repel the radiation or tardigrade-like DNA. In most earthly creatures, DNA is damaged permanently, but with tardigrades, DNA is repairable after being damaged by deadly radiation.[13]
There is a reduced chance of intelligent life on Kepler-737b due to the fair chance that it is a water world, with no dry land.[citation needed] It is likely substantially hotter than Earth, due to its stellar flux 2.297 times that of Earth[3] and resulting equilibrium temperature of 298 K (25 °C; 77 °F).[14] If ice caps exist, then they would likely be much smaller than Earth's, due to the temperature as well as to the possibility that Kepler-737b has more carbon dioxide in its atmosphere than Earth.[a] It would have accreted the carbon dioxide by gravity or because water worlds are likely to have a lot of carbon dioxide in their atmospheres.[citation needed] More carbon dioxide in an atmosphere equalizes the temperature.
See also
Kepler-186f, a habitable zone exoplanet around an early M-star.
Ross 128 b, an exoplanet orbiting a quiet red dwarf.
^"About the Planetary Systems Composite Parameters Table". NASA Exoplanet Archive. Retrieved January 16, 2022. If the Planetary Systems table does not have a value for the planetary radius, mass or density or a stellar luminosity, these values are calculated. See How the Archive Calculates Values in the Planetary Systems Composite Parameters Table for a detailed explanation.
