 Some of the latest imagery and data from NASA's New Horizons probe has changed the way that we look at Pluto. Turns out it's actually an incredibly complex system and one that may actually end up rewriting our planetary geology textbooks. Now this has a lot of people saying that Pluto should be a planet again. And should it? Well, we're going to take a look at that decision to reclassify Pluto in today's space pod, July 24th, 2015. If we want to talk about why Pluto was considered a planet from the outset, then we have to go back to 1930 when Pluto was initially discovered. Clyde Tombow spotted Pluto officially on February 18th, 1930, and at that time it was crowned with a status, Planet. For a few decades of circling in the sun, Pluto held the distinction of smallest, furthest, and least understood planet, and it maintained that multitude of crowns for quite some time. We have to jump forward to the 1990s when developments in optics and computer analysis finally allowed us to begin to search for potential places beyond Pluto. One by one, exoplanets and Kuiper Belt objects began to be found, but it was the Kuiper Belt objects that gave scientists pause. Named after Dutch astronomer Gerard Kuiper, these are mostly icy bodies as close as Neptune's orbit and outward. The first Kuiper Belt object was discovered in 1992, and just over a decade later in 2005, the discovery of an exceptionally large object called Eris put Pluto's planetary status into question. Eris was originally thought to have been somewhat bigger than Pluto, and its measured mass is somewhat larger. Does this mean Eris should be considered the 10th planet? Shortly after two other objects, Homea and Makimake were discovered. Should they be considered planets as well? In science, when we begin to understand something a little bit better, it's not unusual for us to back up and say maybe we rushed into judgment as to what something was, and this is what was happening in the astronomical community in 2005. We began to realize that Pluto, called a planet in 1930, before the Kuiper Belt was even theorized, may not actually be a planet, and very frighteningly, we also didn't have an official definition for what a planet actually was, so we had to come up with one. The International Astronomical Union came together towards the end of 2006 to try and figure out what should be the criteria that makes a planet before things got out of hand. So they came up with three things. The first is that you must orbit the Sun. The second is that you must have enough mass for a hydrostatic equilibrium to occur. That basically means that you're round. And the third is that you must have cleared your orbital neighborhood. Now it's that last one that was a little bit controversial, and is the one that Pluto does not satisfy. Therefore it makes Pluto not a planet. So Pluto was reclassified as a dwarf planet, along with Hamea, Maki Maki, Eris, and Ceres. And the interesting thing about Ceres, upon its discovery in 1801, it was labeled a planet. Then objects like Vesta, Juno, and Pallas were found, and Ceres subsequently lost its planetary status in the 1850s. So, if we're going to call Pluto a planet, then let's call Ceres a planet. Also, let's throw in Vesta, Pallas, and Juno. And why stop there when we can make Hamea, Maki Maki, and Eris planets as well? And suddenly, arguments made from emotional viewpoints of nostalgia suddenly don't end so well. Now do they? Thanks for watching This Space Pod. I'm Jared Head. Let us know what you think about Pluto's reclassification, and if you think it should be a planet again in the comments. And don't forget to comment, like, and subscribe to us on social media. And if you do have a little bit of extra in your wallet, and you can help us out to make more space pods, we do have a Patreon campaign, and every little bit is appreciated. So, until next week, keep exploring.