HD 110067 f is the fifth of six sub-Neptunes around HD 110067, a star a little smaller than the Sun about 100 light-years away. It orbits every 41.1 days and is about 2.6 times Earth's width. With its neighbours it forms one of only a few known chains of six planets in resonance.
Its orbit was found by prediction. A team led by Rafael Luque, using ESA's CHEOPS and NASA's TESS satellites, found that the inner three planets follow a 3 to 2 rhythm and used that pattern to forecast where the outer planets' periods should fall. HD 110067 f sits in a 4 to 3 resonance with e, its inner neighbour: for every four orbits of e, f makes three. The outermost planet, g, sits in the same 4 to 3 rhythm with f.
HD 110067 f is one of three planets in the system with a measured mass, about 5 Earth masses, from the star's wobble, and its signal was among the clearest in those measurements. For a planet about 2.6 times Earth's width, that is a low density, which, the discovery team concluded, suggests a large atmosphere dominated by hydrogen. ESA's Maximilian Günther noted that it is one of only three known six-planet resonant systems, and the second found by CHEOPS. It receives about nine times the light Earth gets from the Sun, far too much for liquid water.