These 80 space trivia questions are great to play with friends, challenge your family with or play by yourself. See how much ...

We have just entered a very favorable period for observing the so-called "elusive" planet Mercury. From now, until about May 13, you should be able to find it with not much difficulty. But how well do ...

The worlds around our sun run the gamut from small and lifeless chunks of rock to gargantuan globes of gas. Our planet's siblings each have its own extreme features and crazy phenomena. -- Charles Q.

Ah, Earth. We may not think about our planet on a day-to-day basis, but the world we live in is a pretty interesting place. The third rock from the Sun—and to this day, the only one with known ...

How far it is from the sun: 886 million miles (1.4 billion kilometers), on average How big it is: 72,400 miles (116,500 km) across, or almost 10 times the size of Earth. How many moons it has: At ...

Mars, the fourth planet from the sun, is a dry, rocky world. Its famous red color has earned it the nickname the Red Planet. Mars has fascinated people throughout history, and today, it is one of the ...