Scientists found an exoplanet almost exactly the same size as Earth orbiting a tiny star not very far away.
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It's called K2-415b, and its similarities (and differences) to our own home world might shed some light on how Earth-like planets form and evolve in different ways, in systems very different from our own.
"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," writes an international team of astronomers led by Teruyuki Hirano of the Astrobiology Center in Japan.
"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 research has been accepted for publication in The Astronomical Journal, and is available on preprint server arXiv.
The exoplanet was first spotted in data from the now-retired Kepler planet-hunting telescope in 2017, and it also appeared in data from Kepler's successor, TESS.
The researchers followed up, taking infrared observations to see if they could detect a faint 'wobble' in the star's motion, as it is ever-so-slightly tugged about on the spot by the gravity of the exoplanet.
This wealth of data revealed the presence of a world, as well as its characteristics. The amount of starlight blocked when the exoplanet transits can be used to calculate the planetary radius. The amount of wobble gives its mass.
Although the exoplanet is about Earth-sized, its mass is much higher, around three times that of Earth. This means that K2-415b is denser than Earth, too.
And it's much, much closer to its star: It has an orbital period of just four days. It's true that the habitable zone of a red dwarf star can be much closer than the Sun's habitable zone, with orbits measurable in days rather than months, but that's a little too close for comfort, even for a red dwarf.
However, only a little. K2-415b sits just inside the rim of K2-415's habitable zone. ■