Until 2015 , Pluto , theformer ninth planetof the authoritative solar system , was largely a mystery — a lilliputian soupcon 3.6 billion miles from the sun . When NASA ’s New Horizons spacecraft get in at the diminutive object in the far - off Kuiper Belt , planetary scientist observe a geologist ’s Disneyland : a intellect - botch humans of steep mess , smooth young surfaces , deoxyephedrine dunes , and a sensational downcast atmosphere .
In 2017 , Mental Floss mouth toKirby Runyon , then a planetary geomorphologist at the Johns Hopkins University Applied Physics Laboratory and a scientist on the NASANew Horizonsgeology team , to learn more . Here is what you call for to know aboutPluto , the minuscule human race with the big heart in the solar system .
One Pluto year equals 248 Earth years.
At 1473 miles in diameter — about half the breadth of the United States — Pluto is the modest of the nine classical major planet and the gravid find “ trans - Neptunian object ” ( an object beyond the planet Neptune ) , though it was demoted todwarf major planet statusin 2006 . As could be expect , it is a freezing -375 ° F on Pluto ’s Earth’s surface . Its gravitational force is about 1/15 that of Earth . It has five Sun Myung Moon : Charon , Nix , Hydra , Kerberos , and Styx . Charon is the largest of themoonsby far , with a diameter about half that of Pluto . It accept rough 248 Earth years for Pluto to circle the sun , and during that time , its highly elliptical orbit takes it as far as 49astronomical unitsfrom our virtuoso , and as close as 30 .
The Disney dog was named after the dwarf planet (not the other way around).
Pluto the not - yet - gnome satellite wasdiscoveredon February 18 , 1930 by astronomer Clyde Tombaugh at the Lowell Observatory in Flagstaff , Arizona . It wasnamedlater that twelvemonth byVenetia Burney , an 11 - year - older girl in England . She first learned of the new , nameless major planet from her grandfather , who cite it while study the newspaper . Burney was concerned in Greek and Romanist mythology at the sentence , and she like a shot suggested Pluto .
Her grandad was impressed , and mentioned it in a note to a friend of his , who taught uranology at Oxford . The astronomy prof passed word to Lowell Observatory , and the astronomers there took an immediate liking to it . It help that the first two letters of Pluto are the initials of the observation tower ’s former father , Percival Lowell . observe that Burney did not get the name from the Disney dog . Just the opposite : The pawl , which premiere the same year as Pluto was discover , was likely named by Walt to ride the planet ’s publicity wave . scientist and cartoonists likewise have yet to explain how the then - unseen planet and cad ended up being more or less the same color .
Technically, a Pluto system space elevator is possible.
Space elevator are a science fiction staple , and advances in carbon nanotubes have made their prospects , if not potential , then certainly potential . The idea is to land a large aim such as an asteroid into a geostationary orbit at Earth ’s equator and link that object and Earth with a cable or social system . You could then rise things into reach without the want for rockets . fit in to Runyon , the unique orbital characteristics of Pluto and Charon create interesting opportunity for the very , very remote future of engineering .
The two world are tidally locked . Charon ’s orbit is on the button the same duration as Pluto ’s rotation , meaning that if you stood on Pluto ’s surface , the synodic month would hover over the same spot , never rising or setting . “ Because they are binary , tidally lock , literally revolve each other in a complete band , you could build a space lift that goes from one planet to the other , from Pluto to Charon , ” Runyon told Mental Floss . “ And it would touch the ground in both places , physically tie them . And you could literally climb a ladder from one to the other . ”
Its “heart” is in the right place.
In 2015 , the New Horizons spacecraft make it at the Pluto system and turned the petty speck into a veridical humans . The famous first image release 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 ’s a view from Pluto ’s higher latitudes , search down . ( The heart , in other words , is higher up on the major planet than the picture suggest . ) Because New Horizons was a flyby craftsmanship and not an orbiter , planetary scientists do n’t know what 40 percent of the planet looks like .
Pluto’s bizarre orbit and rotation are unexplained.
The traditional classroom solar system model of a light bulb as the sun and planets on wire extending from it represents a matt orbital plane lie with as the ecliptic , and for most of the solar system of rules , that ’s pretty tight to the truth . But not for Pluto , which has a 17 - point inclination relative to the ecliptic . Moreover , like Uranus , its gyration is tap on its side , and it rotates back ( east to west ) . No one knows why , according to Runyon . “ It ’s likely the result of an ancient impact , ” he said . “ One not strong enough to interrupt planet but enough to tip on its side . This might have been the Charon - make wallop , which would be like to how our moonlight is formed . ”
Astronomers were wrong about its atmosphere …
astronomer have long known that Pluto has an atmosphere . During stellar eclipse ( that is , when it go in front of stars ) , astronomers can see the star dim , and then wholly go out , and then reappear dimly , and then return to its full luminosity . That dimming is do by the major planet ’s atmosphere . uranologist are further able-bodied to track its concentration over time . Because Pluto is so far from the sun , the frosting on its Earth’s surface sublimates : It goes from a self-colored straight to a gas without first becoming a liquid state . When Pluto reached perihelion ( as close to the sunshine as its gets in an orbit ) in 1989 , the expectation was that the standard atmosphere would begin to collapse entirely : that it would stop dead out , basically , and descend to the open .
“ A good comparison is when it snows on Earth , ” Runyon read . “ Snow is basically the weewee vapor in the atmosphere freezing out and falling to the surface , leave Earth ’s atmospheric denseness slimly scurvy than it would be otherwise . ” In Pluto ’s vitrine , the persuasion was that the double-dyed ambiance would freeze down out and diminish onto the dwarf satellite ’s airfoil .
It did n’t happen . “ Pluto ’s atmosphere is denser than we thought it would be , ” Runyon explicate . “ Even now as it ’s actuate farther from the Sunday , its atmospheric state is bouffant than ever . ” One model pronounce that while the air does flimsy as ices fall to the surface , it never completely freezes and fall .
… which is electric blue.
scientist on the New Horizons team did n’t gestate to see Pluto ’s atmosphere during the flyby . “ When we twirl New Horizons around after skinny approach and attend back at Pluto — being basically backlit from the Sunday — we could see the atm , ” he say . “ We do it we ’d be able to discover it , but to see it , and to see that the dawning and sundown on Pluto is this ethereal electrical blue — nobody previse that . ” Runyon articulate that the New Horizons found discrete atmospheric layers that could be decipher for hundreds of miles . “ Pluto has what ’s called a stably graded standard atmosphere . The coldest bed is on the bottom and it gets warmer as you go up , ” he said .
“ In skill , you test hypotheses , but before you’re able to even do that you take 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 blank space geographic expedition is to see something for the first time , and that ’s what New Horizons was . And to rick around and seem back at the Lord’s Day and see a beautiful atmosphere with the gorgeous layers through it is just astonishing . ”
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A variant of this story was published in 2015 ; it has been updated for 2025 .
