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

Does our Solar System have 9 planets or only 8? Astronomers have gone back and forth on that a lot, with Pluto now being classified as a dwarf planet. However, out beyond Neptune there could be ...

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

All you need to know about planets in our solar system Our solar system is made up of nine planets with Earth the third closest to the Sun. But each planet has its own quirks, so find out more about ...

Scientists believe that two asteroids might be fragments of long-lost "planetary embryos" from the early solar system.

Six of our cosmic neighbors are expected to line up across the night sky tonight, in what has been dubbed a "planetary parade". Throughout much of January and February, Venus, Mars, Jupiter, Saturn, ...

Plate tectonics give Earth its mountains, earthquakes, continental drift and maybe even helped give rise to life itself. But do other planets in the solar system have them too?

All of our solar system’s planets are lining ... in orbital periods between the planets. Mercury, which is closest to the sun, takes about 88 Earth days to complete an orbit, while Neptune ...

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.

such as how on Earth we send signals to planets like Mars in our solar system to talk to rovers and spacecraft. "Any time that two planets are aligned might be interesting," says Tusay.