Kepler-737b

Mass, radius and temperature

Kepler-737b is an exoplanet with 1.96 R_🜨 (0.175 R_J). Its mass is unknown, but is estimated at 4.5 M_E 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 early M-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]

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]

Nomenclature

Kepler-737b is also known as KOI-947.01, KIC 9710326 b, and Gaia DR2 2126820324123177472 b.^[2] KOI means "Kepler Object of Interest" and KIC means "Kepler Input Catalog". Gaia is a European satellite that was launched on December 19, 2013.^[8]

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.

• Kepler-186f, a habitable zone exoplanet around an early M-star.
• Ross 128 b, an exoplanet orbiting a quiet red dwarf.
• TRAPPIST-1, an ultra-cool dwarf with 7 planets, 4 of which are potentially habitable:
  • TRAPPIST-1d
  • TRAPPIST-1e
  • TRAPPIST-1f
  • TRAPPIST-1g
• Gliese 832 c, another Super-Earth exoplanet with a relatively high stellar flux and a small chance of being habitable.^[15]
• Desert planet
• Gliese 1214b, a possible water world.
• Kepler-22b, another possible water world that, unlike GJ 1214b, orbits in the habitable zone.
• Ocean world

• KOI-947.01 in SIMBAD