For over 70 years, there were nine planets in our solar system. From a massive juggernaut like Jupiter to a cool guy with a ring around it like Saturn, we could see all sorts of different planets orbit the sun alongside our home, Earth. The last in line was Pluto, and it was the smallest of the bunch.
It’s now been more than ten years since Pluto was kicked out of the group. Redefining its definition of what makes space objects planets, the International Astronomical Union (IAU) rated its planetary status to a lesser category. We now consider it to be a dwarf planet. But what happened to Pluto, and more importantly — why?
Is Pluto a planet? Well, let’s find out!
Pluto’s Name and Discovery
These days, our former ninth planet roams a dark, shadowy zone, miles away from Neptune’s orbit. Hundreds of thousands of rocky bodies and comets keep it company, with some of these objects broader than 62 miles across. But what’s the history of Pluto? When did we first discover it, and why did we name it the way we did?
Well, back at the beginning of the last century, an American scientist, Percival Lowell, was the first man to officially catch glimpses of Pluto. While observing other planets nearby, he hinted that another planet was lurking behind them. Unfortunately, he died in 1915, without ever pinpointing it. He did, however, suggest its location beforehand.
After Lowell’s death, Clyde Tombaugh finally caught Pluto in 1930. Alongside other experts, he located it using his former colleague’s predictions. Interestingly enough, a young English girl from Oxford is responsible for the dwarf planet’s name. Her idea was to call it after a Roman version of Hades, so her grandpa sent her proposal to the Lowell Observatory, who accepted it.
We remember the dwarf planet fondly. For so long, it was notable for its small size and distance from Earth. Moreover, the United States is larger than Pluto when it comes to width. It lies in the far reaches of our galaxy, the Kuiper’s Belt, with objects like comets and rocky bodies by its side.
You can only see it with a telescope since it’s so far away from us. Furthermore, it orbits more than 3 billion miles from the sun. Some call it the King of the Kuiper Belt because it’s the largest object in that part of our solar system. It’s also pretty interesting that Pluto is the only planet to be discovered while observing from the United States.
Another fascinating fact about this far dwarf planet is that it has five moons. Unlike Earth, Pluto has Charon, Styx, Nix, Kerberos, and Hydra to keep it company during all those cold and dark days in the farthest depths of our solar system. The largest of the bunch is Charon, which is nearly half Pluto’s size and is named after a Greek mythological demon.
And Then There Were Eight
Since Pluto’s orbit overlaps with Neptune’s, the International Astronomical Union doesn’t see it as a planet. For them, planets must meet three basic criteria. They must be a celestial body that orbits the sun. Also, they must have a nearly round shape and a unique orbit. Unfortunately for Pluto, it fails to meet the last demand.
The IAU says that Pluto is a dwarf planet. It also calls it a “Trans-Neptunian Object” which is pretty harsh according to some small planet enthusiasts and schoolchildren who like the idea of nine planets in our orbit. But then again, people find all sorts of things offending, and Pluto’s just another victim of internet outrage. Still, it was all pretty abrupt back in 2006 when scientists made their minds up.
The whole debate about Pluto’s status as a planet began in the early ‘90s. Discovering a small celestial body close to our former ninth planet, astronomers at the University of Hawaii started to speculate whether it’s just one of the planet-like objects that orbit around in the Kuiper Belt. And it didn’t take long for things to change.
In 2003, professor Mike Brown would discover Eris, a similar dwarf-like planet. His discovery inspired scientists to consider that such objects are many, and we regularly mistake them for being planets. These days, people call Brown the man responsible for Pluto’s “planetary” death. Funny, isn’t it?
New Findings and Old Debates
Although we don’t see Pluto as a planet anymore, its story isn’t over just yet. A few years ago, NASA’s spaceship shot photos of the far dwarf planet, which made scientists rethink their former decision. The thing is, Pluto is much bigger than what we initially thought. Moreover, it’s much more interesting and complex.
This discovery is what makes lots of people wonder whether Pluto’s planet status is going to come back to what it was before 2006. There’s much debate about what should come into play when deciding what we deem a planet. And if you ask ordinary folks, Pluto is still a part of our solar system, planet-wise. Back in 2014, one scientific poll showed that most people believe this to be true. Cool, right?
One of the reasons for this debate is that if you look back some 200 years into astronomy, there’s only one document that suggests that a planet needs to have its unique orbit to be an actual planet. Hence, there’s no reason not to change IAU’s standards. It’s simply a sloppy definition if you ask us. There should certainly be more debate over Pluto’s future as the final piece of our galaxy’s jigsaw.