Earth 2.0? Astronomers Spot Similar Exoplanet 72 Light-Years Away

Earlier methods of detecting exoplanets around other stars relied on signs that only larger exoplanets could make, meaning astronomers have only recently acquired the ability to detect near-Earth-sized worlds.

Astronomers believe they have found an exoplanet of near-Earth properties orbiting a red dwarf star 72 light-years away. Dubbed K2-415b, the small world holds much promise for testing new methods of astronomical study.

Their discovery was reported in an article accepted for publication in The Astronomical Journal, but already hosted online at the preprint site ArXiv.

According to their report, the scientists based their conclusions on high-resolution imaging and near infrared spectroscopy of K2-415b. The planet was first detected in 2017 by the Kepler space telescope, the first device built for such a purpose.

They found the planet is rocky and has a mass of between 1.3 and 5.7 Earth masses, with 3 Earth masses being the most likely size. That makes it one of the smallest exoplanets ever discovered.

“Being one of the lowest mass stars known to host an Earth-sized transiting planet, K2-415 will be an interesting target for further follow-up observations, including additional radial velocity monitoring and transit spectroscopy,” the scientists wrote.

M dwarfs, or red dwarfs, are the coolest, smallest, and most numerous type of main-sequence star, and are extremely long-lived. The star K2-415 has just 16% of the mass of our sun.

"Small planets around M dwarfs are a good laboratory to explore the atmospheric diversity of rocky planets and the conditions at which a habitable terrestrial planet can exist," they added.

Smaller exoplanets are harder to spot from Earth than larger worlds using the present detection methods, which look at how planets affect their parent star as they orbit, including wobbling them with their gravity or dimming them as they pass between Earth and the star. However, because dwarf stars are so much smaller than other stars, smaller planets affect them more, which is why most of the rocky worlds discovered thus far orbit red dwarf stars.

While some information can be gathered from planetary orbits, such as their mass and radius, other essential questions still largely evade us about other worlds, including the compositions of their atmospheres. That question is key to determining if the planet can host life: Earth is one of four rocky planets in our solar system, but the only one capable of sustaining life.