The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

All seven of the other planets in our solar system are about to become visible at once in a great planetary alignment – ...

This may explain the strange properties of the orbits of our solar system's planets, which are not quite perfectly circular, and all lie on slightly different planes. NASA artist’s conception of ...

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.

The formation of our solar system from a singular nebula raises an intriguing question: why did each planet develop with a ...