February 18, 1930: Pluto is discovered as the 9th planet around our Sun.
August 24, 2006: Pluto is no longer the 9th planet around our Sun. Now it's a dwarf planet.
Why? What happened? Where Did Pluto Go?
Here’s what happened. Between 1930 and 2006, a lot more objects were found in space. So either they were all planets -- lots and lots and lots of planets -- or astronomers had to come up with a better way to classify them. Unfortunately, under the new definition, Pluto just wasn't large enough to be called a planet any more. Find out more in, Is Pluto A Planet? or in Mark Brown's book where he explains how he inadvertently killed Pluto and why it had it coming.
Many people weren't happy with this change. Read more about why Pluto is so beloved in The Case for Pluto. Last but not least, Neil DeGrasse Tyson tells about the rise and fall of America's favorite planet in The Pluto Files.
But that is so 2006. What's new with Pluto now? We have new pictures! The picture at the top of this page is a mosaic of four pictures that show Pluto in true color, thanks to NASA's New Horizons space probe. Last year, it flew past Pluto and took some amazing photos and even more awesome close-ups.
Add a comment to: Is Pluto Still a Planet? (Hint: No.)