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TOI-733 Exoplanet System

A Planet In The Small-planet Radius Valley Orbiting a Sun-like Star //

TOI-733 is a real G6V yellow dwarf with one known planet, located 246 light years from Earth and belonging to the same family of stars as the Sun. It is slightly smaller at 0.956 solar masses and 0.949 solar radii, and slightly younger at 4.4 billion years old. Its surface temperature is estimated to be 5585 K with 82% of the Sun's luminosity.

Discovered in 2023, TOI-733 b is a hot planet that orbits TOI-733 in just 4.88 days. Researchers constrained its mass and radius to be around 5.72 and 1.992 times Earth, respectively. While these values aren't particularly interesting, more notable is its density of 3.98 g/cm^3, which would place it in the transition region between rocky and gaseous planets that have hydrogen/helium-dominated atmospheres. Modelling suggests that it has a volatile-enriched outer envelope but may also represent a highly irradiated ocean world. In other words, TOI-733 b is an "in-between" planet of the small-planet radius valley, which describes the phenomenon that there seem to be very few exoplanets between the radii of rocky super-Earths and the more puffy mini-Neptunes. Several theories have been proposed, but the origin of this gap is not entirely clear. Thus, further characterisation of TOI-733 b—including determining if it has a secondary atmosphere or is an ocean planet—has broad implications for our understanding of exoplanet evolution and mechanisms of mass loss.

In this simulation, the characteristics of TOI-733 b are replicated from literature wherever possible or inferred in cases of knowledge gaps:

• I've envisioned TOI-733 b as a tidally locked hot mini-Neptune with an average temperature of >900 K.
  
• Based on modelling, a substantial 7.00% of the planet's mass is water, equating to an ocean up to 1200 km deep. The extreme depths and pressure give rise to exotic forms of ice that make up the "seafloor".
  
• The ocean on the day side of the planet is supercritical owing to the high temperature, with no clear boundary between liquid and gas.
  
• As a transitional object between rocky planets and gas dwarfs, TOI-733 b possesses an exceptionally thick atmosphere. For this, I've decided on a turbulent bluish-white design due to the expected occurrence of water, carbon dioxide and methane in this envelope, and unrelenting winds of up to 4000 km/h.

CD-40 6169, 2MASS J10373820-4053179, TOI-733, Gaia DR1 5392408990057860096, CPC 0 8755, PPM 315547, TYC 7714-657-1, CPD-40 4589, SAO 222203, Gaia DR2 5392409372314518656, GSC 07714-00657, TIC 106402532, Gaia DR3 5392409372314518656

• Georgieva, I.Y., Persson, C.M., Goffo, E., Acuña, L., Aguichine, A., Serrano, L.M., Lam, K.W., Gandolfi, D., Collins, K.A., Howell, S.B. and Dai, F., 2023. TOI-733 b--a planet in the small-planet radius valley orbiting a Sun-like star. arXiv preprint arXiv:2304.06655.
  
• Planet toi-733 B (2023) The Extrasolar Planet Encyclopaedia - TOI-733 b. Available at: http://exoplanet.eu/catalog/toi-733_b/ (Accessed: April 19, 2023).