The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

An object eight times the mass of Jupiter may have swooped around the sun, coming superclose to Mars' present-day orbit ...

Simpson and Chen ran mathematical models looking at how differently sized Earth-like worlds would have affected the rest of ...

This places it between Earth and Neptune in a size range that typically divides exoplanets ... expands our understanding of the diversity of planets (just like this strange object in our Solar System) ...

While the composition of gas and dust in a molecular cloud is fairly uniform, everything changes once a star begins to form.

An object we thought belonged to the most common category of planet in the galaxy has turned out to be something we've never seen before.

She mapped our solar system's "alternate fate" had it housed ... When simulating a planet 10 times the size of Earth's mass, Simpson found that the inner planets experienced high obliquity and ...

Stargazers will be treated to a rare seven-planet alignment in February. This is what scientists hope to learn.

The acid yellow moon Io that orbits Jupiter may be less than 30% the size of Earth, but is considered the most volcanic body ...