The search for extrasolar planets resembling Earth constantly yields new finds. Such is the case with HD 137010 b, a candidate recently identified by astronomers. This Earth-sized planet orbits a Sun-like star, in one year.
This identification comes from a detailed analysis of the archives of the Kepler space telescope, whose mission ended in 2018. By continuing to explore this data, researchers spotted HD 137010 b thanks to a single transit observed during the K2 phase. This event, corresponding to the planet passing in front of its star, translates into a slight decrease in brightness that signals its presence.
Artist's concept of HD 137010 b, a candidate rocky exoplanet slightly larger than Earth, orbiting 146 light-years away. Credit: NASA/JPL-Caltech/Keith Miller (Caltech/IPAC)
Several traits of HD 137010 b evoke our own world. Its size is comparable to Earth's and it completes its orbit in approximately one year. Its host star, named HD 137010, belongs to the category of K-type stars, similar to the Sun but somewhat cooler and less luminous. This configuration places the planet near the outer edge of the habitable zone, a region where water could exist in liquid form with an appropriate atmosphere.
Despite this location, calculations show that HD 137010 b could be extremely cold. Its surface temperatures could be around -68 degrees Celsius (-90 degrees Fahrenheit), a value lower than the Martian average. Such cold strongly limits the chances of finding liquid water.
The detection of this planet relies on a single observation, which complicates its confirmation. The transit lasted 10 hours, allowing the orbital period to be approximated, but astronomers need several regular passages to validate its existence. With an orbit as long as Earth's, these events are infrequent, which explains why exoplanets in this category remain rare.
Future instruments could help lift the doubts. NASA's TESS satellite, Kepler's successor, and the European CHEOPS mission are capable of performing complementary observations. In the absence of new data, definitive validation might require next-generation telescopes.
Atmospheric simulations envision several possibilities. According to the study published in
The Astrophysical Journal Letters, HD 137010 b would have between 40% and 51% probabilities of being located in the habitable zone, depending on the definitions used. But a doubt remains about its atmosphere, which could make all the difference.
A thick atmosphere rich in greenhouse gases could thus transform this icy world into a more temperate environment, a hypothesis awaiting testing by subsequent observations.