Just the third-ever confirmed interstellar object has been detected in our solar system. Here's what we know. (Spoiler: It's ...

When most people think of our Solar System, they think of the 8 planets officially recognized by the International Astronomical Union (IAU). But what if I told you there are at least 40 planets, and ...

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, researchers say. ABC News. Live. Video. Shows. Shop. Log In. Stream on.

For a few evenings around 28 February, every planet in the solar system will be visible in the night sky, thanks to a rare great planetary alignment. Here's how to make sure you don't miss this ...

This process, called accretion, is how everything in the solar system – planets, moons, comets and asteroids – came into being. Telescopes can see young solar systems being born.