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 you first learned about the Solar System, you probably saw diagrams that made it look orderly, with planets arranged in circular orbits around the Sun on a flat disk. But in reality ...

Orbits of natural bodies in the universe are usually not perfectly circular — they are elliptical. Some orbits are ever so slightly elliptical (like a somewhat squashed circle, or, in ...

However, it was not until Kepler's observations that the planets followed elliptical orbits around the sun (rather than circular orbits) that astronomical models matched observations of the ...

An object moving in a circular orbit at a constant speed has a changing velocity. This is because velocity is a vector quantity that depends on speed and direction. The object in orbit is ...

But our own Solar System's disc is relatively warped, with the orbits of its planets slightly tilted and more oval than circular. What happened to it? It's possible a heavy object fell into the ...