Add Yahoo as a preferred source to see more of our stories on Google. An interstellar tourist is taking a quick trip through our solar system, becoming one of just three known objects to ever do so, ...

Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

A team of astronomers has identified a four-planet system orbiting the red dwarf star LHS 1903 that defies conventional expectations about how planets arrange themselves around their host stars. The ...

An object eight times the mass of Jupiter may have swooped around the sun, coming superclose to Mars' present-day orbit before shoving four of the solar system's planets onto a different course. When ...

A newly studied solar system breaks the usual planet pattern, raising fresh questions about how rocky and gas planets form.