K. Isogai

A bus schedule drifts: if you don't check it, you'll miss your ride. Planets around other stars have the same problem – their crossings of the star's disk gradually shift. The ExoClock project pooled 30,000 observations from Earth and space to refine the schedule for 620 distant worlds. For 45% of the planets, transits were found to be off by hours.

When a star like the Sun ages, it swells and sheds its outer layers. What remains is a small, dense white dwarf — the former core. Around it, planetary debris can remain: rocks, dust, even whole asteroids. They orbit like a carousel that's been taken apart, but the pieces are still spinning. Astronomers watched the white dwarf WD 1054-226 for six years.