This article was originally featured on The Conversation. Are planets in the solar system that are closer to the Sun older than the ones further away? – Gavriel, age 10, Paducah, Kentucky A cloud of ...

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 ...

PRAGUE, Czech Republic — The universe really is expanding — astronomers are proposing to rewrite the textbooks to say that our solar system has 12 planets rather than the nine memorized by generations ...