NASA confirms a candidate exoplanet, HD 137010 b, in a zone friendly to liquid water

NASA announced in May 2026 that archival data from the Kepler/K2 mission had yielded a candidate exoplanet, designated HD 137010 b, whose size and orbital path place it within the range of Earth-like planets. According to preliminary measurements, the planet has one Earth radius, orbits its host star HD 137010 (146 light-years from the Sun, in the direction of the constellation Lyra) and its orbital period is estimated at between 300 and 550 days. The team, led by astronomer Andrew Vanderburg of the Massachusetts Institute of Technology (MIT), reported that the signal was detected from a single transit lasting about ten hours, which is too short for an unequivocal confirmation.

Methodologically, the discovery rests on the reanalysis of data gathered during the K2 phase of the Kepler mission (2014-2018), when, following the failure of its reaction-wheel system, the telescope observed different parts of the sky in shorter cycles. The team applied a machine-learning algorithm trained to spot “single-transit” signals, that is, transits that earlier algorithms had ignored because they appeared only once within the available window. This approach has, in 2024 and 2025, led to the confirmation of more than 30 candidate exoplanets in the Kepler archive, according to the NASA Exoplanet Archive.

The star HD 137010 is a K-dwarf, meaning it is smaller, cooler and longer-lived than the Sun. According to NASA, this kind of star accounts for about 13 percent of all stars in the Milky Way, but is increasingly regarded as the best candidate for the search for potentially habitable planets, because K-dwarfs are more stable over long timescales than the much more numerous red dwarfs (M-type), which often produce strong flares. HD 137010 has about 70 percent of the Sun’s mass, placing the candidate’s orbit near the outer edge of the so-called habitable zone, the part of orbital space where temperatures allow liquid water on the surface.

What the find shows, and what it does not

The term “habitable zone” does not mean that the planet is actually habitable. It only means that, if it had an atmosphere and if water were present on its surface, it could be in liquid form. Without data on the composition of the atmosphere, which for HD 137010 b we do not have, it cannot be said whether the surface temperature exceeds 0 degrees Celsius or whether the planet has a magnetic field to shield it from the radiation of its host star. Atmospheric spectroscopy, possible with the James Webb telescope only once the planet is confirmed in a second transit, can only be carried out for planets showing a clear repeating signal.

Vanderburg’s team, in a paper published as a preprint on arXiv (still awaiting peer review), say that confirming the candidate would require a new transit, expected anywhere between December 2026 and June 2027, depending on the true orbital period. Observing time has already been booked on the TESS space telescope and on the ground-based HARPS instrument in Chile. If confirmed, HD 137010 b would be one of just a few dozen known Earth-sized exoplanets in the habitable zone.

The limits of the study, which the authors set out themselves, are considerable. First, a single transit in archival data can be the result of random noise, an instrumental glitch or a transit by another astronomical object. Second, the mass of the candidate has not been measured (this requires radial-velocity data for the host star, which means years of ground-based observations). Without the mass, the composition of the planet, and therefore the potential density of its atmosphere, cannot be pinned down. Finally, even if it is confirmed to lie in the liquid-water zone, “potentially habitable” should not be confused with “inhabited”, a distinction astrobiologists consistently confirm in papers published in the journal Astrobiology.