HD 137010 b
Candidate Exoplanet detected by Kepler space telescope
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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, 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.[3] 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.[4] 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][4] Confirmation as a genuine exoplanet requires additional transits or alternative observations, which may be pursued with missions like TESS or CHEOPS.[3][5][6]
Artist's concept of HD 137010 b | |
| Discovery | |
|---|---|
| Discovered by | Kepler (K2)[1] |
| Discovery date | January 27, 2026 |
| Transit | |
| Orbital characteristics | |
| 0.88+0.3 −0.1 AU | |
| Eccentricity | 0 |
| 355.0+200.0 −59.0 d | |
| Inclination | >89.82+0.05 −0.03 |
| Star | HD 137010 |
| Physical characteristics | |
| 1.06+0.06 −0.05 R🜨 | |
| Temperature | 205.0 ± 25.0 K (−68.1 ± 25.0 °C; −90.7 ± 45.0 °F) |
Discovery and observation
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.[3] 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.[3] 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.[3][7]
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".[7][4][2] Venner presented the results at the Rocky Worlds conference, highlighting the planet's Earth-like orbital architecture despite the single-event detection.[3] 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]
Host star
HD 137010 is a K-type dwarf with a visual magnitude of 10.1, making it observable with amateur telescopes.[4] 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.[3]
Characteristics
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.[4] 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.[4] 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][4] No mass or density measurements are available, but its size suggests a rocky composition similar to Earth.[8]
Habitability
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.[4][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.[3] 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.[9]
