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7 Surprising Facts About Pluto

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NASA/JHUAPL/SwRI

Pluto, the ninth planet of the classical solar system was, until 2015, largely a mystery—a few pixels 3.6 billion miles from the Sun. When NASA's New Horizons spacecraft arrived at the diminutive object in the far-off Kuiper Belt, planetary scientists discovered a geologist's Disneyland—a mind-blowing world of steep mountains, smooth young surfaces, ice dunes, and a stunning blue atmosphere. To learn more, Mental Floss spoke to Kirby Runyon, a planetary geomorphologist at the Johns Hopkins University Applied Physics Laboratory and a scientist on the NASA New Horizons geology team. Here is what you need to know about Pluto, the small world with the biggest heart in the solar system.

1. 248 EARTH YEARS = 1 PLUTO YEAR

At 1473 miles in diameter—about half the width of the United States—Pluto is the smallest of the nine classical planets and the largest discovered "trans-Neptunian object" (i.e., an object beyond the planet Neptune). As could be expected, it is cold on Pluto's surface: around -375°F. Its gravity is about 1/15 that of Earth. It has five moons: Charon, Nix, Hydra, Kerberos, and Styx. Charon is the largest of the moons by far, with a diameter about half that of Pluto. It takes about 248 Earth years for Pluto to circle the Sun, and during that time, its highly elliptical orbit takes it as far as 49 astronomical units from our star, and as close as 30.

2. THE DISNEY DOG IS CONNECTED TO THE PLANET.

Pluto the planet was discovered on February 18, 1930 by astronomer Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona. It was named later that year by Venetia Burney, an 11-year-old girl in England. She first learned of the new, nameless planet from her grandfather, who mentioned it while reading the newspaper. Burney was interested in Greek and Roman mythology at the time, and she immediately suggested Pluto.

Her grandfather was impressed, and mentioned it in a note to a friend of his, who taught astronomy at Oxford. The astronomy professor passed word to Lowell Observatory, and the astronomers there took an immediate liking to it. It helped that the first two letters of Pluto are the initials of the observatory's (then dead) founder, Percival Lowell. Note that Burney did not get the name from the Disney dog. Just the opposite: The dog, which premiered the same year as Pluto was discovered, was likely named by Walt to ride the planet's publicity wave. Scientists and cartoonists alike have yet to explain how the then-unseen planet and dog ended up being more or less the same color.

3. A PLUTO SYSTEM SPACE ELEVATOR IS TECHNICALLY POSSIBLE.

Space elevators are a science fiction staple, and advances in carbon nanotubes have made their prospects, if not likely, then certainly possible. The idea is to bring a large object such as an asteroid into a geostationary orbit at Earth's equator, and essentially connect that object and the Earth with a cable or structure. You could then lift things into orbit without the need for rockets. According to Runyon, the unique orbital characteristics of Pluto and Charon create interesting opportunities for the very, very distant future of engineering.

The two worlds are tidally locked. Charon's orbit is precisely the same duration as Pluto's rotation, meaning that if you stood on Pluto's surface, the moon would hover over the same spot, never rising or setting. "Because they are binary, tidally locked, literally orbiting each other in a perfect circle, you could build a space elevator that goes from one planet to the other, from Pluto to Charon," Runyon tells Mental Floss. "And it would touch the ground in both places, physically linking them. And you could literally climb a ladder from one to the other."

4. ITS HEART IS IN THE RIGHT PLACE—THE 40 PERCENT OF THE PLANET WE'VE SEEN.

In 2015, the New Horizons spacecraft arrived at the Pluto system and turned a few pixels into a real world. The famous first image released by NASA is not a straight-on shot from Pluto's side, with the top being the North Pole and bottom being the south. It is in reality a view from Pluto's higher latitudes, looking down. (The heart, in other words, is quite higher up on the planet than the picture suggests.) Because New Horizons was a flyby craft and not an orbiter, planetary scientists don't know what 40 percent of the planet looks like.

5. ITS BIZARRE ORBIT AND ROTATION ARE A MYSTERY.

The traditional classroom solar system model of a light bulb as the Sun and planets on wires extending from it represents a nice flat orbital plane known as the ecliptic, and for most of the solar system, that's pretty close to the truth. But not for Pluto, which has a 17-degree inclination relative to the ecliptic. Moreover, like Uranus, its rotation is tipped on its side, and it rotates backward (east to west). No one knows why, according to Runyon. "It's probably the result of an ancient impact," he says. "One not strong enough to disrupt planet but enough to tip on its side. This might have been the Charon-forming impact, which would be similar to how our moon is formed."

6. WE WERE WRONG ABOUT ITS ATMOSPHERE …

Astronomers have long known that Pluto has an atmosphere. During stellar occultations (that is, when it moves in front of stars), astronomers can see the star dim, and then completely go out, and then reappear dimly, and then return to its full brightness. That dimming is caused by the planet's atmosphere. Astronomers are furthermore able to track its density over time. Because Pluto is so far from the Sun, the ice on its surface sublimates: It goes from a solid directly to a gas without first becoming a liquid. When Pluto reached perihelion (as close to the Sun as its gets in an orbit) in 1989, the expectation was that the atmosphere would begin to collapse entirely: that it would freeze out, basically, and fall to the surface.

"A good comparison is when it snows on Earth," says Runyon. "Snow is basically the water vapor in the atmosphere freezing out and falling to the surface, leaving Earth's atmospheric density slightly lower than it would be otherwise." In Pluto's case, the thought was that the complete atmosphere would freeze out and fall onto the planet's surface.

It didn't happen. "Pluto's atmosphere is denser than we thought it would be," Runyon explains. "Even now as it's moving farther from the Sun, its atmosphere is puffier than ever." One model says that while the atmosphere does thin as ices fall to the surface, it never completely freezes and falls.

7. … WHICH IS ELECTRIC BLUE.

Scientists on the New Horizons team didn't expect to see Pluto's atmosphere during the flyby. "When we spun New Horizons around after closest approach and looked back at Pluto—being basically backlit from the Sun—we could see the atmosphere," he says. "We knew we'd be able to detect it, but to see it, and to see that the sunrise and sunset on Pluto is this ethereal electric blue—nobody anticipated that." Runyon says that the New Horizons found discrete atmospheric layers that could be traced for hundreds of miles. "Pluto has what's called a stably stratified atmosphere. The coldest layer is on the bottom and it gets warmer as you go up," he says.

"In science, you test hypotheses, but before you can even do that you need to figure out what's there in the first place. To me, that's the most exciting part of science. The most exciting part of space exploration is to see something for the first time, and that's what New Horizons was. And to turn around and look back at the Sun and see a beautiful atmosphere with the gorgeous layers through it is just astonishing," he says. 

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Space
Now You Can Train to Be an Astronaut on Your Smartphone
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Just because you don't work for NASA doesn't mean you'll never make it as an astronaut. In the world of private space tourism, a little training could be all you need. And there's an app for that.

Space Nation, a Finnish space tourism startup, recently launched Space Nation Navigator, which the company touts as the first astronaut training app in the world. The app aims to train future space travelers using games, quizzes, and fitness challenges that fall into three categories: "body," "mind," and "social."

Each of the challenges is tailored to help you develop the skills you'd need to survive in space—even the mundane ones. One mission is called "Did you clean behind the fridge?" and is designed to highlight the unpleasant chores crew members on the ISS have to do to keep things tidy. There are "survival" quizzes that test your knowledge of how to properly build a fire, read a map, and dispose of your poop in the forest. The app also plugs into your smartphone fitness data so that you can participate in athletic challenges, like a 650-foot sprint designed to train you to escape a meteor impact zone.

Screenshots of the Space Nation Navigator app
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"Space Nation Navigator offers a way for anyone, anywhere to have a 15-minute astronaut experience every day. These astronaut skills—team building, problem solving, positive life hacks—are not just vital to survive in space," Space Nation CEO Kalle Vähä-Jaakkola said in a press statement. "They are also crucial in your daily life."

New challenges are added to your queue every few hours, and you can compete against other users for high scores. If you get enough points, you can become eligible for real-life training experiences with Space Nation, including a trip to Iceland. In 2019, Space Nation plans to hold an international competition to find one astronaut that the program will send to space.

If you're going to start training, we suggest you take some of the tests Project Mercury applicants faced back in 1958 to see how you'd stack up against the first NASA astronauts.

Get it: iOS, Android

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Big Questions
If Earth is Always Moving, Then How Do We See the Same Constellations Every Night?
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Luis Medrano:

6700 mph is nothing in cosmological speeds and distances. Constellations are freakin’ far away.

Get in a car at night and drive on a straight road, then look at the moon. The angle of the moon in respect to your point of view doesn’t change; it seems like the moon is following you wherever you go. Meanwhile, things that are really close to you—like electric poles, roadside buildings, and trees—seem to fly by really fast.

The effect is known as parallax. Things that are close seem to move faster and “travel more distance” (not really) than things that are far away.

In the video above, there are several objects in perspective. The light in the center, which represents the sun, was placed so far away you can barely see it move.

The sun is only eight light-minutes away; that’s 146 million km on average. At human scale it seems like a lot, but in cosmic distances it is nothing. Orion, for example, has stars that are from 243 to 1360 light years away from us. Imagine traveling at the speed of light for 1360 years. That’s how far these stars are. And these are not even the farthest stars. Some stars are Giga-light years away from us.

Now, with the proper precision instruments you can indeed notice the parallax in distant stars, just not with the naked eye. Furthermore, our solar system has moved so much since the early days of astronomy and astrology, the constellations do not correspond to the early astrology maps. The constellations appear shifted.

As a free info nugget: In case your life is ruled by astrology, whatever sign you think you are, you are not.

This post originally appeared on Quora. Click here to view.

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