As the United States prepares to celebrate its 250th anniversary, the history of the solar system tells its own story 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 ...

For more than a century, people have wondered whether our solar system's planetary count really stops at eight. The idea ...

On August 24, 2006, our solar system lost a planet. It wasn't by cataclysmic destruction, but rather by the vote of the International Astronomical Union, which declared that Pluto, considered the ...