Astronomers have identified a planet candidate, HD 137010 b, that exhibits several Earth-like characteristics, but with a potentially frigid twist: it may be colder than Mars. The discovery, stemming from re-analysis of data collected by NASA’s now-retired Kepler Space Telescope, points to a rocky world orbiting a Sun-like star approximately 146 light-years away.
A Candidate Planet in a Year-Long Orbit
Currently classified as a “candidate,” HD 137010 b requires further observation to confirm its existence. Initial calculations suggest an orbital period of roughly one Earth year, placing it at a comparable distance from its star as Earth is from the Sun. The planet also appears to reside near the outer edge of its star’s habitable zone – the region around a star where temperatures could, theoretically, allow for liquid water on a planet’s surface, provided the atmosphere is suitable.
If confirmed, HD 137010 b would be a significant find. It could become the first Earth-size exoplanet in a year-long orbit observed transiting a nearby, bright, Sun-like star, making it a prime target for more detailed follow-up studies. The transit method, where a planet passes in front of its star from our perspective, causing a slight dimming of starlight, is crucial to these observations.
A Chilling Prospect: Colder Than the Red Planet
Despite the promising orbital characteristics, HD 137010 b receives significantly less energy from its star than Earth does. Scientists estimate it receives less than one-third of the heat and light that Earth receives from the Sun. This is due to the nature of its host star, HD 137010, which, while similar in stellar class to our Sun, is cooler and less luminous.
surface temperatures on HD 137010 b could plummet to as low as minus 90 degrees Fahrenheit (minus 68 degrees Celsius). For context, the average surface temperature on Mars is around minus 85 degrees Fahrenheit (minus 65 degrees Celsius). So the potential Earth twin could be even colder than the Red Planet, presenting a significant challenge to habitability as we currently understand it.
The Challenges of Confirmation
Confirming the existence of HD 137010 b and characterizing its properties, isn’t straightforward. Astronomers rely on detecting multiple “transits” – instances where the planet passes in front of its star, causing a measurable dip in starlight. However, only a single transit event was observed during Kepler’s extended K2 mission. This single event lasted approximately 10 hours, slightly longer than the 13 hours it takes Earth to transit the Sun as viewed from a distant point.
While this initial detection was unusually precise, confirmation requires observing the same event occur again at regular intervals. This is complicated by the planet’s orbital period. Because HD 137010 b orbits at a distance comparable to Earth’s, transits would only occur roughly once per year. Planets with shorter orbital periods transit more frequently, making them easier to detect – a key reason why finding Earth-like exoplanets is so difficult.
Future confirmation efforts may utilize NASA’s Transiting Exoplanet Survey Satellite (TESS) or the European Space Agency’s CHEOPS (CHaracterising ExOPlanets Satellite). If these missions fail to provide conclusive evidence, astronomers may need to await the deployment of more advanced space telescopes capable of gathering additional data.
The Role of Atmospheric Composition
Despite the potentially frigid temperatures, researchers haven’t ruled out the possibility of habitability entirely. Climate modeling suggests that a sufficiently dense atmosphere, rich in greenhouse gases like carbon dioxide, could trap enough heat to allow for the existence of liquid water on the planet’s surface.
Atmospheric simulations estimate a 40% chance that HD 137010 b resides within the “conservative” habitable zone and a 51% chance it falls within the broader “optimistic” habitable zone. However, there remains a roughly 50-50 chance that the planet actually orbits outside the habitable zone altogether.
The findings, published in The Astrophysical Journal Letters on , were the result of work led by Alexander Venner, a Ph.D. Student at the University of Southern Queensland, Australia, who is now a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. The paper is titled “A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2.”
HD 137010 b represents a fascinating, if challenging, target in the ongoing search for potentially habitable worlds beyond our solar system. While its cold temperatures present a significant hurdle, the possibility of a thick atmosphere offering a warming effect keeps the door open to the intriguing prospect of a frozen, yet potentially habitable, Earth analog.
