Erik A. Petigura

Two planets around the star TOI-4495 perform a stumbling dance: while the inner one completes two laps, the outer manages just one. But the rhythm is off — the inner planet speeds up and slows down, like a partner stumbling in her steps. Using the transit method, watching as the planets briefly dim the star's light, astronomers weighed these worlds.

350 light-years away, four planets orbit the star V1298 Tau. They are 5–10 times larger than Earth but lighter than they appear. For nine years, astronomers tracked their motion to understand what they are made of and how they lived in the past. The planets are lined up in a chain: their orbital periods are nearly in 3:2, 2:1, and 3:1 ratios.

The Kepler telescope spent years watching thousands of stars, spotting planets by the tiny dips in starlight when a planet passes in front of its star. Such a passage, or transit, lets us measure the planet's size but not the shape of its path.