Astronomers have identified an unusually low-density exoplanet, TOI-1453 c, orbiting the star TOI-1453, located 250 light-years away in the Draco constellation. The system contains two planets: a super-Earth and a sub-Neptune.
TOI-1453 c is 2.2 times the size of Earth but has a mass of only 2.9 Earth masses, making it one of the least dense sub-Neptunes discovered. Its low density challenges existing models of planetary formation.
Scientists confirmed TOI-1453 c’s existence using NASA’s TESS telescope and the HARPS-N spectrograph. The transit method measured the planet’s size by tracking dips in starlight, while the radial velocity method calculated its mass based on gravitational interactions with its host star.
Researchers suggest two possible explanations for TOI-1453 c’s composition. It may have a thick hydrogen-rich atmosphere, reducing its overall density, or it could be a water-rich planet with a low-density interior, similar to an ocean world.
TOI-1453 b, the inner planet, completes an orbit in 4.3 days, while TOI-1453 c follows a 3:2 orbital resonance, meaning it completes two orbits for every three of TOI-1453 b. This suggests the planets may have migrated from their original formation zones.
TOI-1453 c is a key target for future atmospheric studies. Analysing its composition could improve understanding of sub-Neptunes, a class of exoplanets not found in the Solar System but common in the galaxy.
The James Webb Space Telescope (JWST) is expected to study TOI-1453 c’s atmosphere in detail. Observations could confirm whether the planet has a hydrogen-rich envelope or if it consists primarily of water and other low-density materials.