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 ...

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 ...

If you don’t count Pluto, and the scientific community doesn’t, there are eight planets in this solar system of ours. We know of only one to have life, and we suspect another one might have, at some ...

Mercury, Venus, Earth, Mars...When you hear the names in order, some of you might think, "I learned that in school."But doesn't the Moon belong to that group?Does asteroid just mean a small ...

Over the past 250 years, the number of "planets" in our solar system has ranged from six to nine — and, briefly, even 11 — depending on what astronomers knew at the time and how they defined a planet.