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

It is a question that feels like it should have a straightforward answer: how many planets are there in our solar system? Since Pluto was relegated back down to dwarf planet status, almost everyone ...

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 ...

Our definition of a planet has changed over the years — causing a bit of confusion. | Credit: wasan prunglampoo/Getty Images Over the past 250 years, the number of "planets" in our solar system has ...