Now astronomers have discovered a new Earth-sized exoplanet, TOI-2431 b, which makes its home around the nearby star TOI-2431. This exceptional discovery contributes to the expanding catalog of alien worlds and provides fascinating information about its emerging attributes and dynamics. This unprecedented discovery was only made possible through next-level observational expertise and data analysis.
TOI-2431 b was found to have an astonishingly short orbital period of just 5.4 hours. This staggering pace of travel makes it one of the fastest orbiting exoplanets ever found! It orbits its host star at an incredibly close separation of only 0.0063 astronomical units (AU). For comparison, this distance is more than twice as far as Mercury, the innermost planet in our solar system. The star TOI-2431 is two-thirds the diameter and mass of our Sun. Dating to an estimated two billion years of age, it provides a special context for this new exoplanet.
The host star, TOI-2431, has a metallicity level of -0.02 dex and an effective temperature of about 4,109 Kelvin. Such conditions have important implications for the composition and evolution of both the host star and its planet. TOI-2431 b is probably undergoing tidal deformation since it’s located extremely close to its host star. Because of that, its shortest axis is roughly 9 percent shorter than its longest axis. As a result, the surface of TOI-2431 b is probably molten, powered by its high equilibrium temperature of about 2,000 Kelvin.
TOI-2431 b has a radius of roughly 1.53 times that of Earth. Its mass is even more impressive—6.2 times planet Earth—which provides a mass density of 9.4 grams per cubic centimeter. The planet’s large mass and density suggest that it may have a rocky core. Its intense heat likely prevents the surface from ever solidifying.
TOI-2431 b has an estimated tidal decay timescale of ∼ T d ≈ 31 million years. If the present conditions were to persist, it would eventually fall inward toward its host star. This relatively rapid decay shows just how dynamic these close-in exoplanets can be, bringing into doubt whether or not they’re truly stable in the long term.
To fully characterize TOI-2431 b, astronomers employed some of the best observational techniques available today. To characterize the system, they joined photometric transit data from the Transiting Exoplanet Survey Satellite (TESS), precise radial velocity observations from the NEID and HPF spectrographs, and ground-based speckle imaging with the NESSI instrument.
“We have confirmed the ultra-short period planet TOI-2431 b using a combination of photometric transit data from TESS, precise radial velocity observations with the NEID and HPF spectrographs, and ground-based speckle imaging with the NESSI instrument,” – Kaya Han Taş et al.