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 ...

But this definition of the solar system is considered to be far too simple by some astronomers, such as Caltech's Mike Brown. "It's not really true," Brown told Live Science in an email.

The solar system has many more moons than the one we can see in the sky. ... depends on your definition of a moon. You may like What are dwarf planets — and how many are there?

A new interstellar object, A11pl3Z, has been discovered in our solar system, marking the third such object to be observed. It ...

Planetary scientists are proposing a new definition of a planet to replace one that many researchers view as sun-centric and outdated. The current definition — established in 2006 by the International ...

Many smaller outer solar system objects appear to have orbits that are aligned in certain mysterious ways; the simplest explanation is that their motions are influenced by another, as-yet-unseen ...

Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far into the solar system was touted more than a century ago.

Though Pluto has formally been considered a dwarf planet for almost two decades, it still has many lessons left for planetary scientists — including hints about how the solar system formed.

But in 1850, astronomers actually counted 20 planets in the solar system. 13 of them were asteroids, newly discovered denizens of the region between Mars and Jupiter.

The proposed new definition contains quantifiable criteria that can be applied for defining planets inside and outside our solar system. In the new definition, a planet is a celestial body that: ...