What Size Is Pluto? How Far Is Pluto? (Illustrated)
Pluto is 1,473 miles (2,370 km) in diameter, and its orbit is an average of 3.7 billion miles from the Sun.
To put Pluto size in terms we can imagine, it's a little more than half the width of mainland USA, and just a little shorter than its height. (Mainland United States is 2,680 x 1,582 miles).
Bill Nye Bikes the Solar System
Trying to Visualize the Solar System...
... is like a gnat trying to understand how far it has to fly from Los Angeles to bite someone in New York. The scale is unimaginable. From the gnat's perspective, once it crosses the Rocky Mountains, it could fly for decades before running into anything.
That's why the New Horizons Spacecraft was relatively safe flying at over 30,000 mph for over 9 years to reach Pluto, and it didn't run into anything on the way. Space is so vast, it's practically empty, with planets spread out like dust motes scattered in the void.
Not only is the solar system mindbogglingly huge, but the gaps between things keep increasing as you travel farther out. It's like a hotel lobby with one table in the middle where 4 people cluster around a big lamp, then a chair in the next city, the next state, the next country, the next hemisphere, and on the moon for the next five guests. Even with Pluto's lopsided orbit which brings it right inside the orbit of Neptune (it's just heading out again), it's still billions of miles away.
That's a distance that the human mind isn't adapted to handle. Visualizing cosmic distances didn't help our ancestors figure out a path to the next watering hole or where to put their hand to swat a gnat.
So here's some pictures I've created to show the sizes of planets our Solar System all the way out to Pluto, plus resources by NASA and others that may help if mine don't.
The Sun and Planets to Scale, Illustrated With NASA Images
Above, I scoured NASA for good photos of the Sun and planets, then scaled them all using Pluto's diameter as one pixel. (However, Ceres is too big: it should be less than a pixel).
The right-hand column lists planet diameters. The left-hand column is distance from the Sun at the exact moment of New Horizon's flyby, calculated using NASA's Eyes on the Solar System app.
Planets' orbits are never perfectly circular. Since they're traveling in ellipses, their distance from the Sun varies over time. Pluto, in particular, has an extremely tilted, ellipse-shaped orbit. I could've used average distances from the Sun, but this was more fun.
What about making a map to illustrate those distances? That's tricky. Using the unit of Pluto = 1 pixel, the whole picture would be over 2 million pixels tall. So I divided distances by 200. Or, to put it differently, I multiplied the planets' sizes by 200 to make them visible.
Just one problem: blowing up the Sun x 200 caused it to overlap Mercury and Venus. So I shoved it out of the way and placed a dot where its center should be. Using that point as "zero," the planets are spaced at the correct relative distances to the Sun and each other.
NASA's Simple Model of the Solar System
Follow Light from the Sun Out to Jupiter at the Speed of Light
The Speed of Light As a Measuring Stick
Have you ever wondered why we use "light-years" as distances? That's how far light can travel in a year. Light is really, really fast, but it's not infinitely fast. It takes a tiny snatch of time to leave your phone's screen before it reaches your eye.
In human scale, that lag is too infinitesimal to matter. But across the solar system, it becomes very noticeable.
Light travels at 186,282 miles per second, or 299,792 km per second. You've seen from my map that gaps between planets are millions, or even billions of miles. Radio waves travel at the same speed as light, so sending a signal out to New Horizons actually takes hours to reach it!
The above animation pretends you're a light beam leaving the Sun. You reach the Earth in about 8 minutes, but it takes 43 minutes to reach Jupiter! (Notice the "time until next destination" box at upper right.) That's how long it takes for our Jupiter space probes to talk to us, sending back data at a few K per second at best.
Recommended: LIGHTYEAR.FM, FM Radio's simulation of signals traveling out from Earth year by year— the farther out you go, the older the music!
NASA's Eyes on the Solar System - 3D Virtual Reality App
Other Better Solar System Maps Than Mine
- Our Solar System: A poster & index of best available planet images
Free poster for noncommercial use from Alma College Planetarium. Excellent portraits of planets to scale out to Pluto and Eris, with a small bar across the bottom showing relative distances.
- OMG SPACE (Scrolling map)
FANTASTIC. It not only includes the planets you were taught in school; it also includes the other best-known dwarf planets: Eris (Pluto's twin), Makemake, and my personal favorite, wildly-spinning Haumea.
- Josh Worth's Tediously Accurate Map of the Solar System
Same idea, but more fun: it uses the moon as one pixel, it's a sideways-scrolling to-scale map of the solar system with hilarious commentary to fill wide empty spaces. Only trouble is, it went viral, and the site's getting overwhelmed with visitors.
- All (known) Bodies in the Solar System Larger than 200 Miles in Diameter
A bit out of date: the TNOs are Trans Neptunian Objects, i.e. Kuiper Belt Objects. A lot of them now have names (and moons), and 8 are recognized as dwarf planets as of 2015. But this is still a gorgeous chart.
- xkcd: Surface Area (Cartoon)
"Space Without the Space." This won't help you visualize distances, but it's another way to look at things: the surface area of all known objects in the solar system turned into "countries" on an imaginary map.
Astronomer's "Solar System to Scale" With His Own Photos
© 2015 Ellen