A planet that orbits between a red dwarf and Earth will block out proportionally more of the star's light.
And, because the star is low mass, a planet's gravity will cause it to shift further when it orbits, creating larger Doppler shifts in the light originating from the star.
The new planet, GJ 367b, turned up in data from NASA's Transiting Exoplanets Survey Satellite (TESS) mission.TESS watches for drops in starlight caused by an orbiting planet, and it does so at an impressive clip—the data used here included a new image every two minutes for a total of two weeks.
That's more than enough to pick out the signal caused by GJ 367b, which completes a trip around its star in only a third of a day.
Detection by this method makes GJ 367b an exoplanet candidate; to confirm its existence, the research team turned to an Earth-based telescope, which watched for the Doppler shifts in the star's light caused by the planet's orbit.This confirmed the planet's existence, as the third-of-a-day signal was present (as was a roughly 45-day signal caused by the star's rotation.).
GJ 367b is close enough to be tidally locked with its host star, meaning it rotates once per orbit, keeping a single side facing the star the entire time.The research team fed the stats to an AI trained on other planets, and the AI predicted that GJ 367b has a structure much like Mercury's: a large metallic core taking up much of the interior of the planet, extending over 85 percent of the way to the surface.