Rocky bodies called protoplanets were thought to have formed slightly earlier in the inner solar system than those beyond the ...

An object dubbed 3I/ATLAS is only the third interloper from outside the Solar System seen in all of human history.

Large moons are much more prolific in the outer solar system. Two satellites, Ganymede and Titan, are even bigger than Mercury. But compared to their giant host planets they might as well not exist.

Our Solar System is full of mysteries, but if the inner planets are a puzzle, the boundary between the Solar System and interstellar space is a secondhand puzzle with half the pieces missing.

Despite common assumptions, the disk of our Solar System is warped, and the planets travel around the Sun in slightly eccentric (or oblong) orbits. Scientists now think that a mysterious object ...