All seven of the other planets in our solar system are about to become visible at once in a great planetary alignment – here’s how to spot the celestial show ...

But that includes exoplanets, alien worlds that orbit alien suns. Only eight planets call our solar system home. Or there might still be nine if some astronomers are correct about an as-yet ...

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.