In a system with two known planets, astronomers spotted something new: A small object transiting across the sun-sized star. This turned out to be another planet, which was extra hot and Earth-sized.

The newly spotted planet, called HD 63433 d, is tidally locked, meaning there is a dayside that always faces its star and a side that is constantly in darkness. This exoplanet, or planet outside of our solar system, orbits around the star HD 63433 (TOI 1726) in the HD 63433 planetary system. This scorching world is the smallest confirmed exoplanet younger than 500 million years old. It's also the closest discovered Earth-sized planet this young, at about 400 million years old.