Astronomers have recently discovered an exoplanet, K2-415b, that is almost exactly the same size as Earth and orbits a tiny star not far away from our solar system. The exoplanet’s similarities and differences to our home world might provide important information about the formation and evolution of Earth-like planets in different systems. Teruyuki Hirano of the Astrobiology Center in Japan, who led the international team of astronomers, writes, “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.”
The discovery of K2-415b has been accepted for publication in The Astronomical Journal and is available on the preprint server arXiv. The star K2-415, around which K2-415b orbits, is just 16 percent of the Sun’s mass. The exoplanet was first spotted in data from the now-retired Kepler telescope in 2017 and later confirmed with data from its successor, TESS. Infrared observations showed a faint “wobble” in the star’s motion due to the exoplanet’s gravity, which revealed the planet’s presence and characteristics.
Although K2-415b is approximately Earth-sized, it is much denser, with a mass around three times that of Earth. It has a short orbital period of just four days and is located just inside the rim of its star’s habitable zone. However, it is too close to the star to support life, and the researchers believe the system is more likely to be of interest for exoplanet atmospheric characterization and follow-up surveys looking for other potential life-harboring worlds.
The Milky Way galaxy is full of interesting worlds, but one of the biggest questions humanity has ever asked remains unanswered: why are we here and is there anywhere else in the universe where life could exist? The best population of exoplanets to help answer these questions is small, Earth-sized worlds orbiting nearby small stars. Such planets are the best candidates for characterizing atmospheres because they are more likely to transit between the star and our view, allowing a fraction of the star’s light to pass through the atmosphere and reveal information about its composition.
Around red dwarfs, the habitable temperature zone is closer to the star than around a star like the Sun, making observations easier and more frequent. Small exoplanets are harder to find, but the discovery of K2-415b offers new insight into the potential for life-harboring planets and the conditions for a habitable terrestrial planet to exist.
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