HD 137010 b is an exoplanet candidate detected by the Kepler's K2 mission of NASA.[1] Orbiting the K-type dwarf star HD 137010 in the constellation of Libra, it is located approximately 146 light-years from the Solar System.[1] 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.[2] 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.[3] 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.[1][3] Confirmation as a genuine exoplanet requires additional transits or alternative observations, which may be pursued with missions like TESS or CHEOPS.[2]
Artist's concept animation of the exoplanet candidate HD 137010 b
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.[2] 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.[2] The single transit, lasting approximately 10 hours, was recorded in 2017 and indicated a small planetary body eclipsing its host star.[1] The discovery team, including collaborators from the Max Planck Institute for Astronomy, ruled out false positives such as stellar binaries through detailed modeling.[2][4]
Venner presented the results at the Rocky Worlds conference, highlighting the planet's Earth-like orbital architecture despite the single-event detection.[2] 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).[1]
HD 137010 is a K-type dwarf with a visual magnitude of 10.1, making it observable with amateur telescopes.[3] 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.[1] This dimmer output shifts the habitable zone outward compared to solar-type systems, influencing the thermal environment of orbiting planets like HD 137010 b.[2]
Characteristics
Radius and temperature
The exoplanet's radius is 1.06+0.06 −0.05R🜨, which is 6% larger than Earth's radius. Its semi-major axis is 0.88+0.3 −0.1AU, and its surface temperature can reach –68 °C, which is colder than the average temperature on Mars (–65 °C).[5][6]
A size comparison of HD 137010 b alongside Earth and Mars
Orbit
HD 137010 b has an orbit similar to Earth. The exoplanet's orbital period is 355.0+200.0 −59.0d, which is analogous to the orbital period of Kepler-139 f, and it has an inclination of >89.82+0.05 −0.03 degrees.[7]
Surface conditions
Despite the possibility of a frigid climate, HD 137010 b also could turn out to be a temperate or even a watery world, say the authors of the paper on this exoplanet. It would just need an atmosphere richer in carbon dioxide than our own. The science team, based on modeling of the planet’s possible atmospheres, gives it a 40% chance of falling within the “conservative” habitable zone around the star, and a 51% chance of falling within the broader “optimistic” habitable zone. On the other hand, the authors of the study say the planet has about a 50-50 chance of falling beyond the habitable zone entirely.[6]
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