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

Try stargazing. Need a new idea to keep kids entertained? Try stargazing. Free learning activities and videos about the solar system Free learning activities and videos about the solar system Free ...

With a radius of 2,106 miles, Mars is the seventh largest planet in our solar system and about half the diameter of Earth. Its surface gravity is 37.5 percent of Earth’s. Mars rotates on its ...