HD 137010 b is an exoplanet candidate detected by the Kepler's K2 mission of NASA.^[2] Orbiting the K-type dwarf star HD 137010 in the constellation of Libra,^[3] it is located approximately 146 light-years from the Solar System.^[2] The candidate was identified from a single 10-hour transit event observed during K2 Campaign 15 in 2017, suggesting an orbital period of about 355 days, nearly identical to that of Earth.^[4] With a radius of 1.06 times that of Earth, it is classified as a potential Super-Earth or Earth analog, likely rocky in composition.^[5] Due to its host star's lower luminosity, HD 137010 b receives only about 29% of the incident flux that Earth does, placing it near the outer edge of the system's habitable zone with an estimated equilibrium temperature around −68°C (−90°F), potentially colder than Mars.^[2][5] Confirmation as a genuine exoplanet requires additional transits or alternative observations, which may be pursued with missions like TESS or CHEOPS.^[4][6][7]

HD 137010 b was first flagged as a potential planet candidate by citizen scientists participating in the Planet Hunters project, which sifts through data from NASA's Kepler Space Telescope.^[4] The signal was overlooked by automated detection algorithms, which prioritize multiple transits, until astrophysicist Alexander Venner re-examined the K2 Campaign 15 data during his Ph.D. research at the University of Southern Queensland.^[4] The single transit, lasting approximately 10 hours, was recorded in 2017 and indicated a small planetary body eclipsing its host star.^[2] The discovery team, including collaborators from the Max Planck Institute for Astronomy, ruled out false positives such as stellar binaries through detailed modeling.^[4][8]

The findings were published on January 27, 2026, in The Astrophysical Journal Letters under the title "A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2".^[8][5][2] Venner presented the results at the Rocky Worlds conference, highlighting the planet's Earth-like orbital architecture despite the single-event detection.^[4] Follow-up observations are challenging due to the long orbital period, which reduces the likelihood of repeated transits within a single mission's timeframe, proposed strategies include radial velocity measurements or targeted monitoring with the James Webb Space Telescope (JWST).^[2]

HD 137010 is a K-type dwarf with a visual magnitude of 10.1, making it observable with amateur telescopes.^[5] The star has an effective temperature approximately 1,000 K cooler than the Sun's 5,772 K, resulting in about 70% of the Sun's mass and radius, and correspondingly lower luminosity.^[2] This dimmer output shifts the habitable zone inward compared to solar-type systems, influencing the thermal environment of orbiting planets like HD 137010 b.^[4]

HD 137010 b has an estimated radius of 1.06+0.06
−0.05 R_🜨, placing it in the range of small, potentially terrestrial worlds.^[5] Its orbital period is 355.0+200.0
−59.0 d, with a semi-major axis of 0.88+0.3
−0.1 AU, yielding an nearly circular orbit (eccentricity ≈ 0) and near-edge-on inclination for transit visibility.^[5] The planet receives an incident bolometric flux of 0.29+0.11
−0.13 times that incident on Earth (F⊕), leading to a blackbody equilibrium temperature of roughly −68 °C, though actual surface conditions would depend on atmospheric properties.^[2][5] No mass or density measurements are available, but its size suggests a rocky composition similar to Earth.^[9]

Positioned at the outer boundary of its star's habitable zone as defined by Kopparapu et al. (2013), HD 137010 b may support liquid water under a thick, greenhouse-enhanced atmosphere rich in CO2, potentially resembling a super-Venus or early Martian environment.^[5][2] Atmospheric models indicate a 40% probability of residing in the conservative habitable zone and 51% in the optimistic zone, but a comparable chance of being entirely too cold for surface habitability without extreme greenhouse forcing.^[2] Its proximity to a relatively bright host star facilitates potential spectroscopic characterization of any atmosphere using future observatories like JWST, which could detect biosignatures from subsurface oceans or geothermal activity if present.^[4] However, as an unconfirmed candidate, these assessments remain speculative, and the planet's true nature whether a frozen ice world or marginally temperate awaits validation.^[10]

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Media related to HD 137010 b at Wikimedia Commons

• Anton Petrov (8 February 2026). NASA Missed This! Citizen Scientists Just Found an Earth Like Planet. Video on YouTube.