Our Solar System has eight planets, a few dwarf planets and more than 200 moons. But wait. Are you seeing double? Or did every planet suddenly get a twin? Where would each planet’s double fit in? Why ...

Even the best telescopes can’t see exoplanets. It’s all about watching for jiggly stars, blue shifts, and transits.

When I was a kid, there were nine planets. Now we know of thousands! But that includes exoplanets, alien worlds that orbit alien suns. Only eight planets call our solar system home. Or there might ...

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 ...

There are a couple of ways that scientists can date planets, so which planets formed first in our solar system? When you purchase through links on our site, we may earn an affiliate commission. Here’s ...