TOI-733 Exoplanet System

Hot planet in the "radius valley" orbiting a Sun-like star // TOI-733 is a real G6V yellow dwarf star with one known exoplanet, located 246 light-years from Earth in the constellation Vela. It is slightly smaller than the Sun, with 0. 956 solar masses and 0. 949 solar radii, and slightly younger at 4. 4 billion years old. Its surface temperature is estimated at 5585 K (5312 °C), with a luminosity of about 82% of the Sun's. Discovered in 2023, TOI-733 b is a hot, close-in planet that orbits its host star in just 4. 88 days. Its mass and radius are approximately 5. 72 and 1. 99 times that of Earth, respectively, yielding a density of 3. 98 g/cm³. This places it in the transition region between rocky super-Earths and volatile-rich mini-Neptunes. Its density is too low for a purely rocky composition yet too high for a gas-dominated planet, suggesting a rocky interior overlain by a volatile envelope. Modelling indicates that TOI-733 b likely possesses a volatile-enriched outer layer composed of heavier molecules such as water, carbon dioxide and methane, rather than a primordial hydrogen–helium envelope. With an equilibrium temperature of ~1055 K (782 °C), the planet is strongly irradiated. As such, it may also represent a hot ocean world, though this remains model-dependent. If water-rich, the high temperatures would likely place much of this material in a supercritical state rather than forming a conventional liquid ocean. TOI-733 b lies within the so-called radius valley, a statistical scarcity in the number of exoplanets between compact rocky worlds and more inflated gas dwarfs. This scarcity is commonly attributed to atmospheric loss mechanisms such as photoevaporation or core-powered mass loss. However, recent atmospheric escape modelling suggests that TOI-733 b has experienced only modest mass loss over its lifetime, with estimated losses of approximately 1. 2–4. 8% of its original mass driven primarily by stellar X-ray and ultraviolet irradiation. This implies that the pl