Clues hidden in today’s orbits hint at the violent origins of the solar system — and a rogue giant kicked out long ago.

Exoplanet Kepler-1625b might harbor a moon the size of Neptune—potentially the first confirmed exomoon—but researchers urge caution in interpreting the data.

The Milky Way's two largest companion galaxies may have once been a threesome — but new data from the Gaia satellite leaves the satellites' history an open question.