Which way is ‘down’ has a different answer depending on where you are on Earth, in the solar system, in our galaxy and beyond ...

The orbits of the planets around the Sun have been the source for many a scientific debate. Their current orbital properties are well understood but the planetary orbits have evolved and changed since ...

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 ...

When it comes to planets in our Solar System's habitable zone, one world is too close to the Sun, another is too far and Earth is just right. But maybe things would be different if Venus and Mars ...