Test your knowledge on our solar system, from the biggest and smallest planets to the behemoth mountain on Mars. When you purchase through links on our site, we may earn an affiliate commission.

The solar system is 4.54 billion years old, based on rock dating. Gas giants (Jupiter and Saturn) likely formed first. Ice giants (Uranus and Neptune) probably formed next. Rocky planets formed last, ...

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 as a ...

Stephen has degrees in science (Physics major) and arts (English Literature and the History and Philosophy of Science), as well as a Graduate Diploma in Science Communication. Stephen has degrees in ...

When I was a kid, there were nine planets. Now we know of thousands! But that includes exoplanets, alien worlds that orbit alien suns. Only eight planets call our solar system home. Or there might ...