Oh hello, Pluto!
By the time you read this, New Horizons will have passed the last unseen planet in the solar system. The journey has taken more than 9 years. New Horizons launched from Cape Canaveral atop an Atlas V rocket in 2006, after a speedy 4-year construction. Prior to that, the so-called Pluto Underground spent more than 15 years trying to get NASA to greenlight the project.
Pluto was discovered in 1930 by Clyde Tombaugh, and was originally considered the 9th planet from the Sun.
The name Pluto, after the god of the underworld, was proposed by Venetia Burney (1918–2009), a then 11-year-old schoolgirl in Oxford, England, who was interested in classical mythology. She suggested it in a conversation with her grandfather Falconer Madan, a former librarian at the University of Oxford’s Bodleian Library, who passed the name to astronomy professor Herbert Hall Turner, who cabled it to colleagues in the US.
The object was officially named on 24th March 1930 and was announced on 1st May 1930. Upon the announcement, Madan gave Venetia £5 (equivalent to £282, or $430 USD in 2015) as a reward.
After 1992, its status as a planet fell into question following the discovery of the Kuiper belt, a ring of objects beyond Neptune that includes Pluto among other large bodies. In 2005, Eris, which is 27% more massive than Pluto, was discovered, which led the International Astronomical Union (IAU) to define the term “planet” formally for the first time the following year. In 2006, the IAU reclassified Pluto and its largest neighbours as dwarf planets, leaving Neptune, and not Pluto, the farthest known planet in the Solar System.
Some astronomers believe Pluto should still be considered a planet, though, and now perhaps it will!
At 7:49:58am Eastern on 14th July (Tuesday), the little spacecraft passed Pluto at 7,750 miles, a distance just shy of Earth’s diameter, and the closest it will ever get to the dwarf planet. A few hours later, New Horizons turned back toward the inner solar system and sent a simple message home:
Legend has it that on 14th September 1928, a 26-year-old Walt Disney looked up in the sky and observed a glow unlike he had ever seen before. Disney squinted, and through that squint he saw a planet. Squinting further, he saw on the surface of that planet a silhouette of a dog.
Disney quickly sketched what he saw but kept it secret for several years, until that space rock was observed by the rest of the population.
In January 1930, the planet of Pluto was officially discovered by scientists, and just a few months later in September, a then-nameless cartoon bloodhound would track Mickey Mouse in the The Chain Gang. That dog, of course, was Pluto.
Now, some 31,714 days after Walt Disney first laid eyes on the now-dwarf planet (and 31,192 days after the rest of humanity found out), we finally see what he saw. Pluto’s origins. When NASA released its Instagram-exclusive photo of Pluto, it could’ve rotated it to any angle it wanted (of approximately 360 to choose from). It chose to honour the real founder of Pluto by presenting it as he clearly saw it.
As a dog.
The best thing about the Pluto image from NASA today is the silhouette of Pluto the dog right on it. pic.twitter.com/hVqD5QTwGz
— Scott Johnson (@scottjohnson) July 14, 2015
Mind = Blown pic.twitter.com/jYs2S6S7Az
— Darth Vader (@DepressedDarth) July 14, 2015
But all jokes aside, on Tuesday, the very same day that NASA’s New Horizons Pluto flyby happened, members of NASA’s New Horizons Science Team took to Reddit to answer questions about the mission in an “Ask Me Anything” (AMA) thread.
Here are some things we learned from the AMA:
1. There might be snow on Pluto! But leave the skis at home
Team leader Alan Stern suggested that the dwarf-planet showed signs of snow. But Kelsi Singer, a post-doc on the New Horizons Science Team, gave Redditors the real scoop: “If there was snow, it would be quite frictiony, like skiing on sand, because it is sooooo cold there,” Singer wrote. “It would not be like the snow on Earth, which is actually quite balmy compared to Pluto.”
— NASA Social (@NASASocial) July 14, 2015
Singer’s post had some Redditors reimagining their ski vacations.
2. Pluto has a more youthful complexion than its moon Charon
Images sent back to earth of Pluto’s Texas-sized moon, Charon, revealed a “system of chasms” that NASA claimed is “larger than the grand canyon”. Pluto’s geological features, meanwhile, appear to be much newer.
Why the starkly different surfaces?
Stuart Robbins, a research scientist with the NASA team, replied that the two most likely reasons had to do with Pluto’s size and atmosphere. “Pluto is larger than Charon,” Robbins wrote, “so it can retain more heat and have active geology longer.”
The other? “Pluto has a tenuous atmosphere, and during the 248-year orbit around the sun, the atmosphere sublimates from one area in sun and is deposited in another in darkness, and then this reverses half-way through the orbit,” Robbins explained. “This process is very slow, relatively speaking, but so is cratering.”
3. Getting the spacecraft’s data back to Earth is no easy task
It takes about 4.5 hours for light to travel from Pluto back to the Earth, and according to Robbins, that means a lag in getting data back from the space probe. “It takes over an hour for an image to be played back because of the very slow speeds over such a long distance,” Robbins wrote.
— NASA New Horizons (@NASANewHorizons) July 14, 2015
But that’s nothing compared to total download time for all the data collected during the close encounter. So far, New Horizons has only sent back the tiniest fraction of the data it will collect, but Robbins said that it should all be downloaded in about 16 months.
The mission marks the end of NASA’s bid to explore every planet in the solar system, starting with Venus in 1962. Tuesday’s flyby coincides with the 50th anniversary of the first ever fly-by of Mars by the Mariner 4 probe.
Stay in touch with the New Horizons mission with #PlutoFlyby and on Facebook here.