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

"we can trigger follow-up observations to rule out other possibilities. Astronomers are in fact amazingly good at finding even much lighter objects in our solar system, such as small asteroids ...

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

There may be an undiscovered planet in the outer solar system whose presence is revealed by the strange orbit of objects beyond the eighth planet Neptune. The tantalizing prospect of a ninth ...

She mapped our solar system's "alternate fate" had it housed ... Eccentricity determines the length of each season: lower eccentricity evens out the four seasons into similar lengths, while ...