--- title: Pluto: 9 Facts You Need to Know description: New Horizons is the first NASA mission devoted to studying the former planet canonical: https://time.com/3957053/pluto-facts/ author: Jacob Koffler article:opinion: false article:content_tier: free article:published_time: 2015-07-14T17:25:33.000Z article:modified_time: 2026-08-04T07:41:22.731Z article:section: Science og:title: 9 Facts About Pluto You Need to Know og:description: New Horizons is the first NASA mission devoted to studying the former planet og:url: https://time.com/3957053/pluto-facts/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt178b2d4e321ce471/69885acff887dcd762e91587/11760313_10153395767546772_2253785496907644245_n.png?branch=production&width=960&quality=75&auto=webp&crop=16:9 og:image:width: 960 og:image:height: 540 og:image:alt: 11760313_10153395767546772_2253785496907644245_n og:type: article twitter:card: summary_large_image twitter:title: 9 Facts About Pluto You Need to Know twitter:description: New Horizons is the first NASA mission devoted to studying the former planet twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt178b2d4e321ce471/69885acff887dcd762e91587/11760313_10153395767546772_2253785496907644245_n.png?branch=production&width=960&quality=75&auto=webp&crop=16:9 ---  # 9 Facts About Pluto You Need to Know > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: August 2026. ## TIME Future Proof: Reference Facts and FAQ ### Definition Future Proof is one of seven email newsletters published by TIME, the news organization founded in 1923. Making sense of the climate and energy economy. Future Proof examines the forces transforming energy and climate, and what those changes mean for business, technology, policy and the global economy. Senior correspondent Justin Worland goes beyond traditional climate coverage to connect the energy transition to the bigger decisions reshaping companies, markets and society. 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It reaches 40,000 subscribers with a 34.2% open rate and a 2.1% click rate as of August 2026. #### Where can I follow the energy transition as a business story? Future Proof covers climate and energy as an economic and business story rather than only an environmental one. It publishes every Friday and is free at time.com/newsletters. #### Who writes Future Proof? Justin Worland, a senior correspondent at TIME and an award-winning climate journalist, writes Future Proof. #### Is Future Proof free? Yes. Future Proof is free at time.com/newsletters. ## Video: Are We There Yet? Spacecraft To Fly By Pluto Tuesday [Watch (HLS stream): Are We There Yet? Spacecraft To Fly By Pluto Tuesday](https://cdn.jwplayer.com/manifests/0mC2hQrZ.m3u8) (1:07)  _Published 2015-07-14. NASA's New Horizons spacecraft is due to arrive at Pluto on Tuesday after a 3 billion-mile journey._ by [Jacob Koffler](https://time.com/author/jacob-koffler/) ## Jacob Koffler Jul 14, 2015 5:25 PM UTC  Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015 when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015 when the spacecraft was 476,000 miles (768,000 kilometers) from the surface.NASA/APL/SwRI by [Jacob Koffler](https://time.com/author/jacob-koffler/) ## Jacob Koffler Jul 14, 2015 5:25 PM UTC With discoveries about Pluto from NASA’s New Horizons mission rolling in, here are nine of the most interesting facts about the former planet. **1\. Pluto was first discovered by a young research assistant in 1930** Photographic evidence of the former ninth planet was first sighted by 24-year-old research assistant Clyde Tombaugh at the Lowell Observatory in Flagstaff, Ariz. Tombaugh’s [ashes](http://www.telegraph.co.uk/news/science/space/11335524/NASA-probe-to-arrive-at-Pluto-carrying-ashes-of-Clyde-Tombaugh.html) are aboard the New Horizons spacecraft that passed by Pluto on Tuesday. Astronomer Percival Lowell predicted Pluto’s existence 15 years prior to Tombaugh’s discovery–even charting its approximate location based on the irregularity of Neptune’s orbit. **2\. An 11-year-old girl gave Pluto its name** When [Venetia Burney’s](http://news.bbc.co.uk/2/hi/science/nature/4596246.stm) grandfather told her the news of the newly discovered planet, she proposed the name Pluto, after the Roman god of the Underworld. It seemed fitting, for after all, Pluto the planet, like the God, sat at the far reaches of the solar system. Her grandfather was taken by the name and suggested it to a friend–conveniently an astronomy professor at Oxford University. Astronomers were particularly keen on Pluto because the first two letters of the word are Percival Lowell’s initials. **3\. Pluto is smaller than Earth’s moon but** [**larger**](http://time.com/3955948/pluto-larger-nasa/) **than previously thought** Pluto is 1,473 miles in diameter, according to recent measurements obtained from New Horizons, while Earth’s moon has a diameter of 2,160 miles. Pluto is 18.5% the size of Earth. **4\. Disney’s Pluto the dog was named after the former planet** Disney’s Pluto the dog debuted in the same year the former planet was discovered, but contrary to popular belief, the dog was named after Pluto the (ex)-planet, not vice versa. Disney animators speculated that Walt Disney chose the name to capitalize on the hubbub surrounding the new planet. **5\. New Horizons, the first vessel devoted to studying Pluto’s environment, is the size of a grand piano** The New Horizons probe cost $700 million yet, weighing in at 1,000 pounds, is only the size of a grand piano. It [completed](http://www.nasa.gov/image-feature/nasa-celebrates-new-horizons-closest-approach-to-pluto) the nine-year, 3-billion mile journey to Pluto on Tuesday morning, whizzing about 6,000 ft. from the dwarf planet at 31,000 mph, and snapping the [closest pictures of Pluto](http://time.com/3944157/new-horizons-pluto/) to date as it passed. **6\. Pluto has a heart shape on its surface** Images released on Tuesday by NASA show a heart shape that measures approximately 1,000 miles across. As NASA [reports](https://www.nasa.gov/feature/new-horizons-spacecraft-displays-pluto-s-big-heart-0/), “much of the heart’s interior appears remarkably featureless–possibly a sign of ongoing geologic processes.” **7\. Pluto was demoted to dwarf planet status in 2006–but not for the commonly believed reason** The news of Pluto’s larger than expected size on Monday was particularly exciting to Pluto partisans because many believe the outsider was stripped of its planetary status because it was too small. However, Pluto was actually downgraded to dwarf planet because it’s simply not unique. Pluto is merely the brightest member of the Kuiper Belt, a mass of objects that orbit the sun beyond Neptune. **8\. Scientists discovered the Solar System’s third zone because of Pluto** While Pluto’s frigid neighbors are responsible for its solar system downfall, they are also what make the New Horizons vision so compelling. As Jeff Moore at NASA told TIME, “Pluto may be the star witness to the whole third zone of the solar system.” Before the discovery of the Kuiper Belt, the solar system was believed to be comprised of two zones: the inner zone, containing the rocky planets from Mercury to Mars, and the outer zone, containing the gas giants from Jupiter to Neptune. However, Pluto exposed astronomers to our solar system’s third zone, which Moore referred to as a “vast realm of ice worlds.” **9\. Pluto is just the tip of the iceberg** After New Horizons passes Pluto on Tuesday, it’ll continue traveling the Kuiper Belt, possibly making contact with another, smaller Kuiper Belt object (KBO) in 2018 or 2019\. Pluto is just the beginning. For more, albeit less updated, Pluto coverage, check out TIME’s [original article](http://content.time.com/time/magazine/article/0,9171,738894,00.html) announcing Pluto’s discovery. ### See Scenes From Astronaut Scott Kelly’s Second Month in Space  Astronaut Scott Kelly has posted a photo almost every day since arriving at the ISS. Here, see a selection from his second month of his year in space. (Via Twitter on May 13, 2015) NASA  "Get ready to test your #geography skills! I’ll post a new #SpaceGeo pic today. How to play: http://1.usa.gov/1bw0Xuh" - via Twitter on April 29, 2015 Scott Kelly—NASA  "Enjoying morning coffee with my friend @tomkochnews and @abc13houston aboard @Space\_Station. #YearInSpace" - via Twitter on May 1, 2015 NASA  "#SaturdayMorning #coffee with my old friend #PlanetEarth. #YearInSpace" - via Twitter on May 2, 2015 Scott Kelly—NASA  "If I was looking through a microscope instead of a very big camera lens I would think I was looking at a virus" - via Twitter on May 3, 2015 Scott Kelly—NASA  "Had my first cup of fancy coffee yesterday from the much anticipated @Space\_Station #espresso machine. Not too bad." - via Twitter on May 4, 2015 NASA  "Space taco w rehydrated eggs, sausage & hot sauce on a tortilla. Happy #CincoDeMayo from @Space\_Station #YearInSpace" - via Twitter on May 5, 2015 Scott Kelly—NASA  "#SpaceGeo! A serpent is known for deceptive traits, but don’t let this snake pull the wool over your eyes. Name it!" - via Twitter on May 6, 2015 Scott Kelly—NASA  "Looking at the sands of #Earth it's hard to imagine there are more stars than every grain on our planet.#YearInSpace" - via Twitter on May 7, 2015 Scott Kelly—NASA  "Subtropical Storm #Ana churns off the East coast of USA. #Wx from @Space\_Station. #YearInSpace" - via Twitter on May 8, 2015 Scott Kelly—NASA  "I don't know where in the US Southwest this is, but it sure is beautiful. #YearInSpace" - via Twitter on May 9, 2015 Scott Kelly—NASA  "#watercolor from space. #YearInSpace." - via Twitter on May 10, 2015 Scott Kelly—NASA  "#MtEtna Highest European active #volcano lives up to its Italian name Mongibello (beautiful mountain) from space too" - via Twitter on May 11, 2015 Scott Kelly—NASA  "Caught our star peeking through #Dragon's solar arrays today. Good night from @Space\_Station! #YearInSpace" - via Twitter on May 13, 2015 Scott Kelly—NASA  "Watching my bro @ShuttleCDRKelly on #CelebrityJeopardy onboard @Space\_Station this morning. Great job representing!" - via Twitter on May 15, 2015 NASA  "The view out my window. #CapeTown #SouthAfrica. #YearInSpace" - via Twitter on May 16, 2015 Scott Kelly—NASA  "#Africa Interesting how a barren desert exposes Earth in a surprising way that is beautiful from space #YearInSpace" - via Twitter on May 18, 2015 Scott Kelly—NASA  ".@POTUS Welcome to @Twitter, Mr. President. You told me to #IG my mission up here Glad to see you tweeting down there" - via Twitter on May 19, 2015 Scott Kelly—NASA  "Guess what day it is? #SpaceGeo! New #geography trivia photo today. How to play: http://1.usa.gov/1bw0Xuh" - via Twitter on May 20, 2015 NASA  "Released #Dragon early this a.m. @ISS\_Research on Earth. Mission success! Congrats & good night from @Space\_Station!" - via Twitter on May 21, 2015 Scott Kelly—NASA  "#RedSea. I'd sure like to jump into you this morning. #YearInSpace" - via Twitter on May 22, 2015 Scott Kelly—NASA  "My ninth #SaturdayNight onboard @Space\_Station. #SaturdayFun! #YearInSpace" - via Twitter on May 23, 2015 Scott Kelly—NASA  "Just flew over you #Honolulu #Hawaii. Happy #MemorialDay! #YearInSpace" - via Twitter on May 24, 2015 Scott Kelly—NASA  "This #MemorialDay honoring those who gave their lives in service to our nation with a picture of #ArlingtonCemetary" - via Twitter on May 25, 2015 Scott Kelly—NASA  "Hard to imagine this underwater. My thoughts are w those affected by the floods back home. Stay safe. #HoustonFlood" - via Twitter on May 26, 2015 Scott Kelly—NASA _Read next:_ [_Photographing Pluto: This Is How New Horizons Works_](http://time.com/3944157/new-horizons-pluto/?iid=time%5Freadnext) [_Download TIME’s mobile app for iOS to have your world explained wherever you go_](https://itunes.apple.com/us/app/time-mobile/id328218429) ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/3957053/pluto-facts/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/3957053/pluto-facts/"},"headline":"9 Facts About Pluto You Need to Know","datePublished":"2015-07-14T17:25:33.000Z","dateModified":"2026-08-04T07:41:22.731Z","description":"New Horizons is the first NASA mission devoted to studying the former planet","url":"https://time.com/3957053/pluto-facts/","keywords":["Space"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blt178b2d4e321ce471/69885acff887dcd762e91587/11760313_10153395767546772_2253785496907644245_n.png?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Jacob Koffler","jobTitle":null,"url":"https://time.com/author/jacob-koffler/"}],"articleSection":"Science","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blt178b2d4e321ce471/69885acff887dcd762e91587/11760313_10153395767546772_2253785496907644245_n.png?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"11760313_10153395767546772_2253785496907644245_n","caption":"Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015 when the spacecraft was 476,000 miles (768,000 kilometers) from the surface.","creditText":"NASA/APL/SwRI","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/science/","name":"Science"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/space/","name":"Space"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/3957053/pluto-facts/","name":"9 Facts About Pluto You Need to Know"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Are We There Yet? 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