Using NASA’s Transiting Exoplanet Survey Satellite (TESS), an international team of astronomers has discovered an extrasolar planet orbiting TOI-4616—a nearby M-dwarf star. The newfound alien world, which received designation TOI-4616 b, is slightly larger than Earth. The finding was reported in a research paper published March 11 on the arXiv pre-print server.
Launched in 2018, TESS is in the process of scanning about 200,000 of the brightest stars near the sun, searching for potential transiting exoplanets. To date, it has identified more than 7,900 candidate exoplanets (TESS Objects of Interest, or TOI), of which 760 have been confirmed.
Nearby M dwarf draws attention of planet seekers
One of the stars observed by TESS is TOI-4616—an M dwarf of spectral type M4 at a distance of some 91.8 light years away from Earth. TESS has identified a transit signal with a period of approximately 1.5 days in the light curve of this star. Now, follow-up observations of TOI-4616 conducted by a group of astronomers led by Francis Zong Lang of the University of Bern, Switzerland, have validated the planetary nature of this transit signal.
“We report the discovery and statistical validation of TOI-4616 b, an Earth-sized planet transiting a nearby mid-M dwarf observed by TESS. We confirm the planetary nature of the signal and determine the system parameters by combining TESS photometry with ground-based multi-band transit observations, high-resolution imaging, and optical/near-infrared spectroscopy,” the researchers explained.
The properties of TOI-4616b and its host
According to the paper, TOI-4616 b has a radius of approximately 1.22 Earth radii and its mass is estimated to be between 1.5 and 3.0 Earth masses. The planet orbits its host every 37.2 hours and its equilibrium temperature is at a level of 525 K.
Based on the derived parameters, the astronomers assume that TOI-4616 b is a rocky world and classified it as an Earth-sized planet orbiting a mid-M dwarf. They note that TOI-4616 and its newly found exoplanet could serve as a valuable benchmark system for comparative studies of terrestrial planets around mid-M dwarfs.
The researchers suppose that TOI-4616 b has its primordial hydrogen/helium envelope efficiently stripped, while its compact secondary atmosphere may have survived. They note that transmission spectroscopy with the James Webb Space Telescope (JWST) could potentially detect atmospheric features of TOI-4616b if it retains a secondary atmosphere.
When it comes to the properties of the parent star, it is about 19% the size and mass of our sun. It has an effective temperature of 3,150 K, metallicity of about -0.32 dex, and its age is estimated to be 300–800 million years. https://phys.org/news/2026-03-tess-earth-sized-planet-orbiting.html
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