5 Numerical Fun Facts About Pluto
How far away is Pluto? How many years does it take to fly there? How long does Pluto take to orbit the Sun? How fast is it traveling? And how fast is the New Horizons spacecraft on its way to Pluto traveling? Keep on reading to find out!
July 14, 2015 is shaping up to be a very exciting day here on Earth. Because, of course, it’s Bastille Day! But although that will be lots of fun for many people, it’s not the real reason for my exuberance. That instead stems from the fact that on that day, I and the rest of the science-loving world will be glued to the Internet watching humanity’s first close encounter with the famous former planet Pluto.
This mission to such a distant world is truly incredible. And there are a ton of incredible numerical fun fact questions about the mission and the dwarf planet, too. For example, how far away is Pluto from Earth? How long does it take us to get there? How many years does it take Pluto to orbit the Sun? How fast is it moving in its orbit? And how fast is the New Horizons spacecraft moving? Those questions—and their numerical fun facts answers—are exactly what we’ll be talking about today.
Fact #1: How Far Away Is Pluto?
As you probably know, Pluto is no longer considered to be the ninth planet of our solar system. And contrary to what a lot of people think, I think Pluto is rather happy about that. Because instead of being the smallest regular old planet, Pluto is now classified as one of the largest dwarf planets. Pretty cool for Pluto, right? Truthfully, that whole classification thing doesn’t really matter much. Pluto is still Pluto, which means it’s still a fascinating place way out in the boonies of our solar system.
Pluto is currently about 32 times as far away from Earth as Earth is from the Sun.
Which leads us to our first numerical fun fact for today: Pluto is currently about 32 times as far away from Earth as Earth is from the Sun. As it turns out, Pluto’s orbit is much more elliptical than the nearly circular orbits of the solar system’s eight regular planets (which is one of the many ways that Pluto sticks out in the crowd). As a result, Pluto’s distance from the Sun changes significantly over the course of its orbit—from about 30 times the typical Earth-Sun distance up to about 50 times this distance. Or, in more familiar Earthly units, from about 2.75 billion miles up to about 4.5 billion miles. So, yeah, Pluto is indeed way out there in the boonies.
Fact #2: How Long Does Is Take to Fly to Pluto?
Given how far away Pluto is from Earth, you might imagine that it takes a long time to get there. And your imagining would be spot on. No matter what your mode of transportation, the journey from Earth to Pluto is a long one. Even for light (which moves faster than anything else), the trip is no picnic. In fact, it takes light almost 4.5 hours to complete the journey! Since radio waves are a form of light, this means that it takes about 4.5 hours for any communications to be sent to or from the New Horizons spacecraft that’s on its way to the dwarf planet.
Speaking of this spacecraft, it was launched to Pluto on January 19, 2006 (back when Pluto was still classified as a regular planet) atop an Atlas V rocket. This rocket hurtled the New Horizons probe into space with a higher speed than anything else ever launched in human history. And yet because Pluto is so far away, it has still taken nearly a decade for New Horizons to complete its journey. For comparison, if we instead had to make the journey at the typical cruising speed of a passenger aircraft (about 550 miles per hour), it would have taken about 6 centuries to make the trip.
Fact #3: How Long Is a Year on Pluto?
Pluto is a weird place. Actually, we don’t know a whole lot about Pluto since it’s so far away and hard to observe. Remedying this situation is kinda why we’re heading there! But we do know a number of things—for example, the properties of its orbit around the Sun. As we noted earlier, the average distance between Pluto and the Sun is about 40 times farther than the average distance between Earth and the Sun.
Every human alive is less than 1 Pluto year old.
Those of you who know a bit of astronomical history will know that a very famous guy named Kepler discovered long ago (in the early 1600s) that the time a planet takes to go around the Sun is related to how far away it is from the Sun. In particular, he found that if you measure the distance at which a planet orbits the Sun relative to the typical Earth-Sun distance (the latter of which is a distance known as 1 Astronomical Unit or 1 AU), then if you cube this distance and finally take the square root of the result, you’ll end up with the number of years it takes the planet to complete a lap around the Sun. For Pluto and its roughly 40 AU orbit (roughly 40 times the typical Earth-Sun distance), this corresponds to an orbital period of around 250 years! So every human alive is less than 1 Pluto year old.
Fact #4: How Fast Is Pluto Moving?
Given that Pluto is really far from the Sun compared to the Earth and that it takes so many years for it to complete one orbit, you might wonder how fast it’s moving. But before we get to Pluto, let’s take a minute to ask the same question of our beloved Earth. How fast are we traveling around the Sun during Earth’s yearly odyssey?
If you do the math and divide the distance Earth travels during a complete orbit (584 million miles) by the time it takes to complete this orbit (1 year or around 30,000,000 seconds), you’ll find that Earth is moving at almost 20 miles per second or about 65,000 miles per hour. Pretty fast. How about Pluto? Again, if you do the math and divide the distance it travels during a complete orbit (22.7 billion miles) by the time it takes to complete this orbit (about 250 years), you’ll find that Pluto is moving at “only” about 3 miles per second or roughly 10,400 miles per hour. Why so slow compared to Earth? Well, way out in the boonies where Pluto roams, the Sun’s gravitational pull is much weaker and therefore swings Pluto around at a much more leisurely pace.
Fact #5: How Fast Is New Horizons Moving?
We’ve seen that the New Horizons spacecraft left Earth faster than anything has before, and we’ve seen that it had to travel a tremendous distance to reach its destination, which leads to the question: How fast has it been traveling on its way to that destination? The answer is fast—really fast—about 9 miles per second or 32,400 miles per hour! Amazingly, this means that New Horizons is traveling towards Pluto much faster than Pluto is traveling around the Sun!
New Horizons is traveling towards Pluto much faster than Pluto is traveling around the Sun!
As I said at the outset, this really is an incredible mission. So, you’ll definitely want to stay tuned to the astronomy news over the next few weeks to see what we find. And be sure to check out next week’s Ask Science episode to learn more about all the exciting science that’ll be happening when New Horizons finally arrives at (and then keeps on flying right by) the famous dwarf planet Pluto.
Wrap Up
OK, that’s all the astronomically themed numerical fun facts we have time for today.
For more fun with math, please check out my book, The Math Dude’s Quick and Dirty Guide to Algebra. And remember to become a fan of The Math Dude on Facebook, where you’ll find lots of great math posted throughout the week. If you’re on Twitter, please follow me there, too.
Until next time, this is Jason Marshall with The Math Dude’s Quick and Dirty Tips to Make Math Easier. Thanks for reading, math fans!
Pluto and New Horizons image from Shutterstock.
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About the Author
Jason Marshall is the author of The Math Dude’s Quick and Dirty Guide to Algebra. He provides clear explanations of math terms and principles, and his simple tricks for solving basic algebra problems will have even the most math-phobic person looking forward to working out whatever math problem comes their way.
