TOI-1453 system hosts contrasting super-Earth and low-mass sub-Neptune

TOI-1453 system hosts contrasting super-Earth and low-mass sub-Neptune
by Erica Marchand
Paris, France (SPX) Mar 17, 2025

Astronomers have identified two planets orbiting the star TOI-1453, located approximately 250 light years from Earth in the constellation Draco. The system, which includes a super-Earth and a sub-Neptune, provides an intriguing opportunity to study planetary types that are prevalent across the galaxy but missing from our own solar system. The discovery offers promising avenues for future exploration of planetary atmospheres and formation mechanisms.

TOI-1453 resides in a binary star system and is marginally smaller and cooler than the Sun. Around it, two distinct planets have been detected: TOI-1453 b, a rocky super-Earth, and TOI-1453 c, an unusually light sub-Neptune. These classes of planets, while absent from the solar system, are among the most frequently observed in the Milky Way, making this discovery particularly significant for comparative planetary science.

The research team employed data from NASA's Transiting Exoplanet Survey Satellite (TESS) alongside observations from the HARPS-N spectrograph to uncover and characterize these planets. "The two planets present an interesting contrast in their characteristics," stated Manu Stalport, astrophysicist at the University of Liege and lead author of the study. TOI-1453 b is slightly larger than Earth and likely consists mainly of rock, completing an orbit around its star every 4.3 days. TOI-1453 c, in contrast, measures about 2.2 times Earth's diameter but has a remarkably low mass of only 2.9 Earth masses, making it one of the least dense sub-Neptunes yet found.

To confirm these findings, the astronomers used two complementary techniques. The transit method, based on TESS observations, allowed them to determine the planets' sizes and orbital periods by detecting minor dips in the star's brightness as the planets passed in front. Additionally, radial velocity data from HARPS-N provided insights into the planets' masses by tracking shifts in the star's motion induced by gravitational interactions.

"All these observations have revealed that TOI-1453 c is extremely light for its size, suggesting that it could have a thick hydrogen-rich atmosphere or a composition dominated by water. This makes it an ideal candidate for future atmospheric studies," enthuses Manu Stalport. Understanding their formation and evolution could provide clues about the development of planetary systems, including our own."

Another compelling aspect of the system is the near 3:2 orbital resonance between the two planets. This means that for every three orbits of TOI-1453 b, TOI-1453 c completes nearly two. Such configurations are believed to result from orbital migration, shedding light on the dynamic processes that shape planetary systems over time.

The discovery positions TOI-1453 c as a prime target for advanced telescopes, such as the James Webb Space Telescope (JWST), to examine its atmosphere in greater detail. Determining whether its low density arises from a hydrogen-dominated envelope or a water-rich interior could enhance our comprehension of sub-Neptune formation and evolution.

Research Report:TESS and HARPS-N unveil two planets transiting TOI-1453. A super-Earth and one of the lowest mass sub-Neptunes