TESS Finds Earth-Sized Planet Around Nearby M-Dwarf
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- TOI-4616 b was discovered by NASA's TESS as an Earth-sized exoplanet transiting the M4 dwarf star TOI-4616, located approximately 91.8 light-years from Earth.
- Francis Zong Lang of the University of Bern led the international team that statistically validated the planet, combining TESS photometry with ground-based multi-band transit observations, high-resolution imaging, and optical/near-infrared spectroscopy.
- TOI-4616 b measures approximately 1.22 Earth radii with an estimated mass of 1.5–3.0 Earth masses, completes an orbit every 37.2 hours, and has an equilibrium temperature of 525 K.
- TOI-4616 — the host star — is roughly 19% the size and mass of the Sun, has an effective temperature of 3,150 K, metallicity of about -0.32 dex, and an estimated age of 300–800 million years.
- The researchers concluded that TOI-4616 b is likely a rocky world whose primordial hydrogen/helium envelope was efficiently stripped, and noted that JWST transmission spectroscopy could detect atmospheric features if a compact secondary atmosphere survived.
- The team flagged the TOI-4616 system as a potential benchmark for comparative studies of terrestrial planets around mid-M dwarfs, and the finding was posted to the arXiv pre-print server on March 11.
Why it matters: TESS has now flagged more than 7,900 candidate exoplanets, with 760 confirmed — and each new nearby, Earth-sized world narrows the hunt for habitable rocky planets around small stars. At 91.8 light-years away, TOI-4616 b is close enough that JWST could realistically test whether a planet stripped of its primordial envelope can still hold onto a secondary atmosphere, a key question for M-dwarf habitability.
