7 Surprising Facts About Pluto

NASA/JHUAPL/SwRI
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. 

10 Reusable Gifts for Your Eco-Friendliest Friend

Disposable tea bags can't compete with this pla-tea-pus and his friends.
Disposable tea bags can't compete with this pla-tea-pus and his friends.
DecorChic/Amazon

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By this point, your eco-friendly pal probably has a reusable water bottle that accompanies them everywhere and some sturdy grocery totes that keep their plastic-bag count below par. Here are 10 other sustainable gift ideas that’ll help them in their conservation efforts.

1. Reusable Produce Bags; $13

No more staticky plastic bags.Naturally Sensible/Amazon

The complimentary plastic produce bags in grocery stores aren’t great, but neither is having all your spherical fruits and vegetables roll pell-mell down the checkout conveyor belt. Enter the perfect alternative: mesh bags that are nylon, lightweight, and even machine-washable.

Buy it: Amazon

2. Animal Tea Infusers; $16

Nothing like afternoon tea with your tiny animal friends.DecorChic/Amazon

Saying goodbye to disposable tea bags calls for a quality tea diffuser, and there’s really no reason why it shouldn’t be shaped like an adorable animal. This “ParTEA Pack” includes a hippo, platypus, otter, cat, and owl, which can all hang over the edge of a glass or mug. (In other words, you won’t have to fish them out with your fingers or dirty a spoon when your loose leaf is done steeping.)

Buy it: Amazon

3. Rocketbook Smart Notebook; $25

Typing your notes on a tablet or laptop might save trees, but it doesn’t quite capture the feeling of writing on paper with a regular pen. The Rocketbook, on the other hand, does. After you’re finished filling a page with sketches, musings, or whatever else, you scan it into the Rocketbook app with your smartphone, wipe it clean with the microfiber cloth, and start again. This one also comes with a compatible pen, but any PILOT FriXion pens will do.

Buy it: Amazon

4. Food Huggers; $13

"I'm a hugger!"Food Huggers/Amazon

It’s hard to compete with the convenience of plastic wrap or tin foil when it comes to covering the exposed end of a piece of produce or an open tin can—and keeping those leftovers in food storage containers can take up valuable space in the fridge. This set of five silicone Food Huggers stretch to fit over a wide range of circular goods, from a lidless jar to half a lemon.

Buy it: Amazon

5. Swiffer Mop Pads; $15

For floors that'll shine like the top of the Chrysler Building.Turbo Microfiber/Amazon

Swiffers may be much less unwieldy than regular mops, but the disposable pads present a problem to anyone who likes to keep their trash output to a minimum. These machine-washable pads fasten to the bottom of any Swiffer WetJet, and the thick microfiber will trap dirt and dust instead of pushing it into corners. Each pad lasts for at least 100 uses, so you’d be saving your eco-friendly friend quite a bit of money, too.

Buy it: Amazon

6. SodaStream for Sparkling Water; $69

A fondness for fizzy over flat water doesn’t have to mean buying it bottled. Not only does the SodaStream let you make seltzer at home, but it’s also small enough that it won’t take up too much precious counter space. SodaStream also sells flavor drops to give your home-brewed beverage even more flair—this pack from Amazon ($25) includes mango, orange, raspberry, lemon, and lime.

Buy it: Amazon

7. Washable Lint Roller; $13

Roller dirty.iLifeTech/Amazon

There’s a good chance that anyone with a pet (or just an intense dislike for lint) has lint-rolled their way through countless sticky sheets. iLifeTech’s reusable roller boasts “the power of glue,” which doesn’t wear off even after you’ve washed it. Each one also comes with a 3-inch travel-sized version, so you can stay fuzz-free on the go.

Buy it: Amazon

8. Countertop Compost Bin; $23

Like a tiny Tin Man for your table.Epica/Amazon

Even if you keep a compost pile in your own backyard, it doesn’t make sense to dash outside every time you need to dump a food scrap. A countertop compost bin can come in handy, especially if it kills odors and blends in with your decor. This 1.3-gallon pail does both. It’s made of stainless steel—which matches just about everything—and contains an activated-charcoal filter that prevents rancid peels and juices from stinking up your kitchen.

Buy it: Amazon

9. Fabric-Softening Dryer Balls; $17

Also great for learning how to juggle without breaking anything.Smart Sheep

Nobody likes starchy, scratchy clothes, but some people might like blowing through bottles of fabric softener and boxes of dryer sheets even less. Smart Sheep is here to offer a solution: wool dryer balls. Not only do they last for more than 1000 loads, they also dry your laundry faster. And since they don’t contain any chemicals, fragrances, or synthetic materials, they’re a doubly great option for people with allergies and/or sensitive skin.

Buy it: Amazon

10. Rechargeable Batteries; $40

Say goodbye to loose batteries in your junk drawer.eneloop/Amazon

While plenty of devices are rechargeable themselves, others still require batteries to buzz, whir, and change the TV channel—so it’s good to have some rechargeable batteries on hand. In addition to AA batteries, AAA batteries, and a charger, this case from Panasonic comes with tiny canisters that function as C and D batteries when you slip the smaller batteries into them.

Buy it: Amazon

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Don't Miss Saturn And Jupiter's Great Conjunction on the Winter Solstice

Paul Williams, Flickr // CC BY-ND 2.0
Paul Williams, Flickr // CC BY-ND 2.0

In 2020, skygazers were treated to meteor showers, a new comet, and a Halloween blue moon. One of the last major astronomical events of the year is set to fall on the night of the winter solstice. On December 21, look up to catch Saturn in conjunction with Jupiter.

What is the conjunction of Saturn and Jupiter?

In astronomy, a conjunction occurs when two planets appear exceptionally close in the night sky. Two of our solar system's gas giants will share a celestial "kiss" on the longest night of the year. The rare meeting of Saturn and Jupiter is known as the "great conjunction" by astronomers.

Though conjunctions between the planets are fairly common, Saturn and Jupiter only get together once in a generation. Their last conjunction happened 20 years ago in the year 2000. Even if you were around for the last one, 2020's planetary meet-up is worth catching. Saturn and Jupiter will come within 0.1° of each other, or about one-fifth the width of a full moon. The last time the two planets came that close was in 1653, and they won't match that proximity again until 2080.

How to see the conjunction of Saturn and Jupiter

Saturn and Jupiter have been inching closer throughout October and November. You can find them now by looking for Jupiter, currently the brightest planet in the night sky, right after sunset. Saturn will appear just east of Jupiter as a dimmer planet with a golden hue.

As autumn wanes, the two planets will gradually bridge the space between them until they reach conjunction on winter solstice. On Monday, December 21, the planets will be so close that they may form a coalescence. That happens when the light from two planets appear to shine as a single star. When that happens, the super-bright body will be easy to spot.