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

Watch this video to find out more about the Earth, planets in our Solar System and other planets far ... Some are the size of small stones and pebbles. Some measure hundreds of kilometres across.

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.

ISTOCK / GETTY IMAGES PLUS The planets in our solar system orbit the sun in roughly the same plane, known as the ecliptic, which is tilted relative to Earth's equator by about 23.5 degrees.

The team’s simulations allowed for four, five or size planets ... in which our own solar system formed. But early such clusters are tumultuous places. In a dense cluster, planets will become ...

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

As the planets align in relative proximity to one another in our field of view, they offer researchers unique conditions to study their interactions and behavior within the solar system.

"Relatively small planets similar to the size of Earth are ... There are nearly 300 moons in our solar system, but their masses are typically much smaller relative to their host planets than ...

All of our solar system’s planets are lining up to parade through the night sky at once. This extraordinary celestial event will see the sky scattered with seven visible planets in what is known ...