HD 50554 c is a hot super-Earth found crossing in front of a Sun-like star that was already known to host a giant planet on a wide orbit. HD 50554, an F-type star a little hotter than the Sun about 100 light-years away, has a cold giant known from the star's wobble. HD 50554 c circles far closer in, every 5.97 days, and is about 1.3 times Earth's width.
It was validated in 2026, together with its sibling HD 50554 d, by a team led by Quanyi Liu. They were testing an idea about how planetary systems form: whether stars with a giant planet far out are more likely to have small planets close in. They searched NASA's TESS data for transits around 132 stars already known to host cold giants, and HD 50554 turned up two transiting candidates, which they confirmed as planets using the TESS light curves, archived measurements of the star's wobble and positions from the Gaia satellite.
Across their sample, they found that stars with cold giant planets host hot super-Earths about six and a half times as often as other stars, and estimated that about 91 percent of such systems have at least one. HD 50554 c is one of the planets behind that result. Its mass has not been measured; the NASA Exoplanet Archive's figure is an estimate. It receives more than 300 times the light Earth gets from the Sun, so it is far too hot for liquid water.