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Quickie Questions - Other Solar System Stuff - Pluto and Its Moon

Date Answered Questioner (age, location) Question Answer

January 14, 2010Mitchell (age 10, United States) When is Pluto going to have an actual picture? You can find some in our web page Pluto Image List .
January 7, 2010Madison (age 11, USA) How fast does Pluto rotate???:) Pluto's Rotation Period about Axis (length of Pluto's day) is 6.387 Earth days.
January 5, 2010Valerie (age 17, NC) Is Pluto apart of our solar system? Yes!, Pluto was just reclassified as a Dwarf Planet. More information in our web page Pluto demoted - no longer a Planet!.
October 8, 2009sheena (age 24, south Carolina) Which one of these planets has never been visited by a satellite or probe, Neptune, Saturn, Uranus, or Pluto? Pluto has never been visited by satellites or probes.
September 28, 2009thalia (age 16, California) Are there any Unusual Features of pluto?? There are some features that set Pluto appart. First, the inclination of its orbit around the Sun is more than any other planet — 17 degrees. Second, when Pluto is closest to the Sun, it is inside Neptune's orbit (and because the tilt of its orbit, it will never collide with Neptune). Third, all other planets from the Earth outward have a day of no more than 25 hours, but Pluto's day is about 6.4 of our days.
September 16, 2009julie (age 13, england) how far away are the dwarf planets from the earth Pluto, one of the dwarf planets, has a minimum distance from the Earth of 28.6 AU (4.28 billion km or 2.66 billion miles).
September 16, 2009julie (age 13, england) How far away are the dwarf planets from the sun pluto, one of the dwarf planets has a minimum distance from the Sun of 29.66 AU (4.437 billion km or 2.757 billion miles).
September 15, 2009molly (age 11, qld) How much does pluto weigh? It has been calculated that Pluto's mass is 12.5 x 1021 kilograms (0.0021 x Earth's)
August 20, 2009Katrina (age 11, victoria) what is the landscape of pluto.... i need to know now Data from 1999 suggests that the surface of Pluto is made of two different parts. It has an icy part and a non-icy part (the non-icy part may be some sort of rock). Scientists are fairly certain the icy part is made of frozen nitrogen, but also contains smaller amounts of frozen carbon monoxide and methane. Pluto is so far away that is it very hard to see the planet, so we can't yet tell how much of the surface is covered with ice, and how much is covered with something which is not ice (the possibly rocky part). It will take a mission to Pluto to sort some of these things out!
August 18, 2009Katrina (age 11, Australia) what is the legth of pluto's orbit around the sun? Pluto's revolution period about the Sun (length of Pluto's year) is 248 earth's years.
August 17, 2009victoria (age 9, FL North Port) In what ways is Pluto like other planets? Pluto has been officially demoted from its status as a planet. The International Astronomical Union (IAU), at a meeting in August 2006, voted on their first "official" definition of a planet. Based on this new definition, Pluto is no longer a planet. According to the IAU's definition, our Solar System has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. In the new scheme, Pluto will be one of several "dwarf planets" in the Solar System; but "dwarf planets" are not considered true planets. See mre information in our web page Pluto demoted - no longer a Planet!.
August 7, 2009MCKENZIE (age 11, n.c) what is the length of day on pluto The rotation period of Pluto about its axis (length of Pluto's day) is 6.387 Earth's days.
August 7, 2009alexis (age 12, N.C) who named pluto? It was Venetia Phair, when she was just 11 years old, who suggested the name. Here is an interview with Venetia.
August 6, 2009mckayla (age 10, colorado) when did pluto change from a planet to a star? Plutois still a planet, it was just reclasified as a dwarf planet (very different from a star).
May 18, 2009chynna (age 11, New Jersey) Is pluto a real planet?? Yes, it is! Pluto was just reclasified as a Dwarf Planet.
April 30, 2009Claudine (age 13, Philippines) Why does neptune and pluto overlap each other? Pluto has the most eccentric orbit of all the planets in the solar system. Its orbit takes it to 49.5 AU (7.4 billion kilometers) at its farthest point from the Sun. And its orbit takes it as close as 29 AU (4.34 billion kilomters) to the Sun. That means that Pluto's orbit draws within the orbit of Neptune, as can be seen in this drawing, making Pluto the 8th planet rather than the 9th planet for roughly 20 years at a time. Pluto was the 8th planet from January 1979 to February 1999. Neptune is now the 9th planet for over 200 years!
April 15, 2009Long (age 8, Pa USA) what is inside Pluto Pluto is mostly made of ice, with a small core of some rocky material buried inside. More details in our web page Pluto's Interior.
March 25, 2009henry (age 11, kentucky/united states) what planet has the longest year Pluto completes a revolution about the Sun (length of Pluto's year) in 248 Earth years.
February 25, 2009abyi (age 10, VA) wath is the diameter of pluto Pluto's diameter is 2,390 km (1,485 miles) [0.187 x Earth's].
February 19, 2009john (age 11, texas) what is the size of pluto Pluto has a diameter of 2,390 km (1,485 miles) and a mass of 12.5 x 1021 kilograms (0.0021 x Earth's).
February 18, 2009Lily (age 11, Canada) What is the surface like on Pluto? Data from 1999 suggests that the surface of Pluto is made of two different parts. It has an icy part and a non-icy part (the non-icy part may be some sort of rock). Scientists are fairly certain the icy part is made of frozen nitrogen, but also contains smaller amounts of frozen carbon monoxide and methane.
February 6, 2009Wesley (age 11, Canada) If you weighed 100 pounds, how much would you weigh on Pluto? Pluto's surface gravity is 0.58 m/s2 (0.06 x Earth's), then, a 100 lbs object on earth would only weight 6 lbs on Pluto.
January 23, 2009camila (age 12, Connecticut) How come Pluto has no Atmosphere? It may seem hard to believe that Pluto could have an atmosphere because it is so cold at 39 AU, where Pluto is found, but it does. Because there are times when Pluto is closer to the sun than is Neptune (making it the 8th planet for roughly 20 years at a time), ices on Pluto's surface evaporate and form an atmosphere. It is continually produced and lost again as long as Pluto is inside Neptune's orbit. The air is made mostly of nitrogen gas, just like that of the Earth and Saturn's moon Titan, with the addition of carbon monoxide (CO - what comes out of your car) and a molecule called methane.
November 6, 2008Alistair (age 10, scotland) how far is it from earth to pluto Pluto minimum distance from Earth is 28.6 AU (Astronomic Units) = 4.28 billion km or 2.66 billion miles. More interesting facts in our webpage Pluto Statistics.
November 3, 2008Candice (age 28, USA) My daughter's teacher told her that Pluto has dissolved. I told my daughter it did not dissolve but it's a dwarf planet. Am I correct or the teacher? You are. Pluto was just reclassified as a Dwarf Planet. You can point your daughter to our web page Pluto demoted - no longer a Planet!.
October 9, 2008JESSICA (age 12, ARIZONA) WHY IS PLUTO CALLED A DWARF PLANET A "dwarf planet" is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite. This definition describes Pluto.
October 9, 2008Estephenie (age 11, Calexico) Did pluton disapear? No, Pluton did not dissapear, it was just reclassified as a "Dwarf Planet"
August 19, 2008Ava (age 11, New hamshire) Why is Pluto not a planet any more? :( The The International Astronomical Union (IAU) redefined "planet" in the Solar System and created a new class, the "dwarf planets". A "dwarf planet" is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite. This definition describes Pluto.
August 18, 2008Logan (age 12, USA) Is Charon's core made of iron? Currently there are two main theories about Charon's internal structure: some scientists believe it to have a rocky core and an icy mantle (like Pluto)while others believe Charon to be of uniform composition throughout.
August 15, 2008Davis (age 10, California, Irvine) Why is pluto's orbit is tilted? Scientists don't know for sure the reason for Pluto's orbit to be so tilted. Some think that it was due to a catastrophic event, like an impact, or that Pluto was previously a moon of Uranus or Neptune and was dislodged from its orbit.
July 7, 2008chelsea (age 11, nc/whittier) What is the teperature range for pluto? Pluto's surface temperatures are -233° to -223° C or -387° to -369° F )
July 3, 2008Anna (age 11, ) What is the name of Pluto’s moon? Charon, Pluto's moon, was discovered by James Christy on 22nd June 1978.
June 23, 2008Jessica (age 12, L.A.) What do the temperatures range from, on Pluto? The temperatures in Pluto's surface range from -233° to -223° C or -387° to -369° F.
April 29, 2008Karma (age 19, MN USA) the pluto's aphelion & perihelion distances ?Which planet in our solar system has the least eccentric orbit? Maximum Distance from Sun (aphelion): 49.31 AU (7.376 billion km or 4.583 billion miles). Minimum Distance from Sun (perihelion): 29.66 AU (4.437 billion km or 2.757 billion miles).
April 15, 2008Rehma (age 12, Pakistan) The planet Pluto has been considered one of the planets for the past 78 years so how can they exclude it and whats the point of doing that?we have been studying this since 78 years? The The International Astronomical Union (IAU) redefined "planet" in the Solar System and created a new class, the "dwarf planets". A "dwarf planet" is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite. This definition describes Pluto. For more information you can visit the IAU website.
April 10, 2008Tirzah (age 14, Minnesota) Why was pluto voted out of the planet catagory since nobody can live on any planet in the Milky Way exepct earth? There was only a reclasification of the bodies in the solar system. Pluto is now a "dwarf planet".
April 2, 2008mackenzie whiteman (age 10, kentucky) what is 1 fact about pluto? Few facts about Pluto: Diameter: 2,390 km (1,485 miles) Mass: 12.5x1021 kilograms (0.021 x Earth's) Density: 1,750 kg/m3
March 18, 2008tiffany (age 15, flordia.USA) are their any canyons,or mountains on pluto?? Pluto is so far away that is it very hard to see the planet, so we can't yet tell how much of the surface is covered with ice, and how much is covered with something which is not ice (the possibly rocky part). It will take a mission to Pluto to sort some of these things out!
March 5, 2008sonia (age 12, colrado) how far is pluto from the sun? Pluto maximum distance from Sun is 7.376 billion km or 4.583 billion miles. Its minimun distance is 4.437 billion km or 2.757 billion miles.
February 25, 2008Matthew (age 14, Colorado USA) How does the atmosphere of Pluto change from its position farthest from the the sun to its position nearest to the sun? There is not a lot of information about Pluto, but scientists have found that it seems as if the planet's thin atmosphere has cooled over the past years while the surface seems to be getting warmer. Some changes are expected as Pluto moves away from the Sun, but the cooling/warming picture is way more complex that expected.
February 25, 2008Matthew (age 14, Colorado Springs, Colorado USA) How does the atmosphere of Pluto change from its position farthest from the the sun to its position nearest to the sun? There is not a lot of information about Pluto, but scientists have found that it seems as if the planet's thin atmosphere has cooled over the past 14 years while the surface seems to be getting warmer. Some changes are expected as Pluto moves away from the Sun, but the cooling/warming oicture is more complex.
February 5, 2008david (age 14, uk) is charon a moon or dwarf planet Our web page Pluto & Charon, a double planet? discusses if Charon is Pluto's moon, or if it is a binary planet.
January 10, 2008vedant (age 10, india) is pluto still a planetor not?why? The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. Two new definitions were also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.”
January 1, 2008colby (age , ) Pluto´s gravity has been caalculated to be 0.58 m/s2, which is 0.06 times Earth's gravity. The same proportion will hold for your weight.
December 21, 2007Isabelina (age 10, Florida) what does pluto look like up-close???????????????? Pluto is the only planet in our Solar System not yet viewed close-up by spacecraft.
December 20, 2007Justine (age 12) When was pluto discovered? Pluto was discovered by Clyde Tombaugh of the Lowell Observatory by comparing a photographic plate taken on the night of January 23, 1930 with two others taken in the same month.
December 17, 2007AMARI (age 10, MISSISSIPPI) WHO DISCOVERED THE PLANET PLUTO? Pluto was discovered by Clyde Tombaugh of the Lowell Observatory by comparing a photographic plate taken on the night of January 23, 1930 with two others taken in the same month.
December 17, 2007Sydney (age 10, Missouri) What is the climate on pluto? Pluto's atmosphere is similar to that of Neptune's moon Triton. On Triton there are seasons and winds. Because Pluto has a bigger atmosphere than Triton, there may even be clouds and storms. However, seeing these clouds and winds on Pluto is difficult.
September 19, 2007Tahlia (age 12, QLD) what does pluto orbit a star or a planet Pluto is a dwarf planet orbiting the Sun, our star.
September 17, 2007Darrian (age 13, Nebraska) is it true what there saying about Pluto
Its nolonger a planet?
It is true, Pluto is now considered a Dwarf Planet. A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite.
September 17, 2007hailey (age 10, ) why does pluto get so cold couln't the sun warm it up a bit because the sun is in the middle of our solar system. It is a matter of distance to the Sun. For example, our planet reach a minimum distance from Sun of 146 million km (91 million miles), while Pluto's minimum distance from Sun is 4.437 billion km (2.757 billion miles)... a huge difference!
September 17, 2007hailey (age 10, ) why does pluto get so cold couln't the sun warm it up a bit because the sun is in the middle of our solar system. It is a matter of distance to the Sun. For example, our planet reach a minimum distance from Sun of 146 million km (91 million miles), while Pluto's minimum distance from Sun is 4.437 billion km (2.757 billion miles)... a huge difference!
July 10, 2007Christine (age 15, Iowa) Why is Pluto not known as a Planet anymore? I read different theories that said that Pluto is known as a planet. Lat year all of a sudden some group of scientists decide that they want to not include Pluto a planet anymore. That concludes my question. Actually Pluto is still a planet, but is now considered part of a new group labeled "Dwarf Planets".
July 2, 2007ross (age 12, kansas USA) why does pluto have a orbit but is not a planet? Because it lies now within a new classification: Dwarf Planets.
May 22, 2007charlie drew (age 9, s,c usa) did pluto really get kicked out of the solar system? Not really. Pluto was reclasified as a "Dwarf Planet", a new classification established by the International Astronomical Union (IAU).
April 19, 2007andreina (age 11, canada) what is pluto made of?? Data from 1999 suggests that the surface of Pluto is made of two different parts. It has an icy part and a non-icy part (the non-icy part may be some sort of rock). Scientists are fairly certain the icy part is made of frozen nitrogen, but also contains smaller amounts of frozen carbon monoxide and methane.
April 19, 2007Aheli (age 12, India) Why Pluto is not considered as planet The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.”
April 13, 2007Karla (age 9, Louisiana) What is Pluto made of? Data from 1999 suggests that the surface of Pluto is made of two different parts. It has an icy part and a non-icy part (the non-icy part may be some sort of rock). Scientists are fairly certain the icy part is made of frozen nitrogen, but also contains smaller amounts of frozen carbon monoxide and methane. Pluto is so far away that is it very hard to see the planet, so we can't yet tell how much of the surface is covered with ice, and how much is covered with something which is not ice (the possibly rocky part). It will take a mission to Pluto to sort some of these things out! More information in our web page Pluto.
April 4, 2007kellie (age 12, teaxas) Why is pluto considered adwarf planet The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. From these definitions, Pluto is now considered a "dwarf planet"
March 27, 2007Toni (age 18, Indiana) How old exactly? and What is pluto's relative mass? Pluto's mass is 12.5 x 1021 kilograms (0.0021 x Earth's). Pluto has about the same age as the Sun: 4.5 billion years.
March 27, 2007lolo (age 9, ga) What does pluto mean? From the Roman myth: Pluto is the god of the underworld in ancient mythology; brother of Zeus and husband of Persephone. Visit our web site Pluto for more about the legend.
March 23, 2007Laksmi (age 11, Phillipines) why does they declare that pluto is not a planet? Dwarf Planet is a new definition in the lastest clasification of the International Astronomical Union (IAU): A "dwarf planet" is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite. Pluto characteristics correspond to this definition.
March 23, 2007Laksmi (age 11, Phillipines) why does they declare that pluto is not a planet? Dwarf Planet is a new definition in the lastest clasification of the International Astronomical Union (IAU): A "dwarf planet" is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite. Pluto characteristics correspond to this definition.
February 28, 2007lawson (age 11, victoria) is pluto still considered a planet The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.”
February 12, 2007AUDRIANNA (age 18) WHAT HAPPEND TO PLUTO? Pluto is still rotating around the Sun in the same orbit as always. Pluto was just reclasified as a "Dwarf Planet".
February 5, 2007carla (age 13, usa) how many rings does pulto and mars have? Mars and Pluto do not have rings, but they have moons: Mars has two moons: Phobos and deimos. Pluto has 3 moons, Charon (very large) and other two fairly small moons: S/2005 P1 and S/2005 P2.
January 23, 2007Sam (age 10, Kentucky/United States) If you don't classify Pluto as a dwarf planet would you classify it as one of Neptune's moons? No, Pluto's orbit is around the Sun. Neptune's moons orbit around Neptune.
January 22, 2007Jonathan (age 11, Ontario, Canada) How long does it take pluto to orbit the sun? Pluto's revolution period about the Sun (length of Pluto's year) is 248 years.
January 14, 2007Danielle (age 11, California) How can scientists be sure that Pluto is not a planet? The demotion of Pluto is related to the most recent definition of "planet" by the International Astronomical Union (IAU): (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.”
January 3, 2007aubrey (age 13, lancaster s.c) how long it takes pluto to turn one time on its axis? Pluto's rotation period about its axis(length of Pluto's day)is 6.387 Earth days.
December 27, 2006Aadhithya (age 5, Michigan/USA) I need to submit soloar system diagram to my school, so I would like to know whether I should include pluto planet as 9th planet in my diagram or I should draw only 8 planets excluding pluto? Please advise me. The answer of your question lies in the new definition of "planet": The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.” For more information you can visit the IAU website: http://www.iau.org/
December 27, 2006simar (age 13 years, INdia) what was the reason behind the disappearance of pluto? Pluto has not dissapeared, just the definition of "planet" changed: The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.” For more information you can visit the IAU website.
December 27, 2006Haneefa (age 10, Kentucky) Why do you call Pluto A dwarf planet when Earth is about 8.46 times smaller than pluto The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.”
December 27, 2006katie (age 9, co) why is pluto not a planet The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From these definitions Pluto belongs to the second group, the “dwarf planets.”
December 11, 2006Victoria (age 11, Massachusetts, U.S.A.) What is the radius of Pluto? Pluto's diameter is 2 390 km (1 485 miles) [0.187 x Earth's].
December 9, 2006Ronaliza (age 16, Philippines) What is the new name of Pluto? PLuto is now considered a dwarf planet, but is keeping his name.
December 6, 2006esbeydy (age 11, az) why is pluto not a planet any more The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From this definitions Pluto belongs to the second group, the “dwarf planets.” For more information you can visit the IAU website: http://www.iau.org/
December 1, 2006Evelin (age 10, California /Los Angeles) Is Pluto still a planet? The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects orbiting the Sun, except satellites, are now known collectively as "Small Solar System Bodies". From this definitions Pluto belongs to the second group, the “dwarf planets.” For more information you can visit the IAU website: http://www.iau.org/
November 27, 2006Stephanie (age 10, Pennsylvania) Why is Pluto no longer a planet but it still orbits our sun?????? Because the new definitions are based in different criteria: The International Astronomical Union (IAU) redefined "planet" and other objects in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From this definitions Pluto belongs to the second group, the “dwarf planets.” For more information you can visit the IAU website: http://www.iau.org/
November 14, 2006hasnain (age 13, new york city) why pluto isn't a planet The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite. (3) The rest of the objects, except satellites, orbiting the Sun are now known collectively as "Small Solar System Bodies". From this definitions Pluto belongs to the second group, the “dwarf planets.”
November 14, 2006Gina (age 11, Mississippi / United States) What is the rotation period for Pluto? The period of rotation of Pluto about its axis (length of Pluto's day) is 6.387 days. For more interesting facts about Pluto visite our page Pluto.
April 4, 2003 Craig (age 10, Texas, USA) Since the sun is a star, I would think that even though Pluto is very far from the sun, it would be close enough to other stars to have at least some heat. Why doesn't it? Even though Pluto is very far from our Sun, it is not very far away compared to even the closest star. Pluto is about 39 AU from our Sun (a little less than 6 billion kilometers). The nearest star, Alpha Centauri, is about 4.3 light years away (about 41 trillion km). So Alpha Centauri is almost 7,000 times farther from our Sun than Pluto! Pretend your head is our Sun, and hold out your arm. If Pluto was in your hand, Alpha Centauri would be about 2 miles away. So even though Pluto is very far away, it is not very close to even the nearest star. So other stars do not heat Pluto.
February 3, 2003 Jamie (age 29, Michigan, USA) If we were to bounce light to the planet Pluto, how long would it take to reach Pluto and return back to Earth again?

The distance between Earth and Pluto varies as the two planets move around their orbits. When they are closest, they are about 29 A.U. apart; at most, the distance is about 51 A.U. Since light travels about 300,000 kilometers each second, it would take light anywhere between 8 hours and 14 hours to make the round-trip journey to Pluto from Earth.

Radio signals travel at the same speed as light. If you were using radio signals to control a robot on Pluto, you would have to be very patient. If you sent your robot a command to move, the command would arrive at least 4 hours later. Then, if your robot took a picture and sent it back to Earth, it would take at least 4 more hours before you could see that picture!

August 30, 2002 Jacqueline (age 10, California, USA) Is Pluto a planet? Other people have wondered that same question! According to the The International Astronomical Union, it is still a planet, but the subject has been much debated!

July 23, 2001 Justine (10, California, USA) If Pluto was made a planet, then does it revolve around the Sun like every other planet, even though it's too cold and too far away from the Sun? Pluto is in fact still designated a planet, and it does revolve around the Sun like the other planets.
June 6, 2001 Jill (9, Michigan, USA) For how many years do Neptune and Pluto switch orbits? Pluto was the eighth planet from the Sun from February 7th, 1979, through February 11, 1999 (so for about 20 years!). Now, Pluto will remain the ninth planet through the 23rd century.
May 14, 2001 Kerrie (13, Pennsylvania, USA) Where can I find information on Pluto? (Hades) Here's a page on the planet Pluto and here's a page on the mythology of Pluto.
July 19, 2000 Donald (age 25, Wyoming, USA ) Percival Lowell believed that the irregularities in the motion of the planet Uranus were due to a planet beyond Neptune. His efforts and the efforts of others that followed led to the discovery of what?

Lowell's persistance led to the discovery of the planet Pluto! The ninth planet was finally discovered by astronomer Clyde W. Tombaugh in 1930.

June 23, 2000 Cate (age 12, New York, USA ) Is Pluto a terrestrial planet or a gas giant? The inner planets (Mercury, Venus, Earth, Mars) are called terrestrial planets because they have thin atmospheres in comparison with their large rocky and icy solid interiors. In moving outward beyond Mars and the asteroid belt, we enter a region of very different planetary composition.

The next four planets are considered gas giants (Jupiter, Saturn, Uranus, Neptune). But, Pluto doesn't really fit in either category. It is a small, rocky planet, but it is located far beyond Mars! It is actually most similar to a group of objects called Trans-Neptunian Objects (TNOs), or asteroids.

So, as you can see, Pluto doesn't really fit in the terrestrial/gas planet distinction.

August 2, 1999 Amy (age 12, California) Is it true that Netune is also the farthest planet because it's orbit crosses with pluto's? Neptune became the last planet on Feburary 7th 1979, but But Pluto regained the title of last planet on Feburary the 11th of this year (1999). The reason for this flip flop is Pluto's eccentric orbit which caries the tiny frozen world between 7.4 and 4.4 billion km's away from the Sun. Pluto will remain the ninth planet for over two hundred years.
June 17, 1999 Cheska (age 16, Philippines) Which planet lies not on the plane of orbit of the other planets in the Solar System? Pluto's orbit has an inclination of 17.14 degrees. Because of the inclination and highly eccentric orbit of Pluto scientists think that it might have been captured by the Sun's gravity sometime after the formation of the rest of the solar system.
February 25, 1999 Kodey (age 9, New Hartford, Iowa) What color is Pluto? Since Pluto is so far away, we don't have very much information about it yet. The next planned mission to Pluto should bring back more information about the planet, including its color.
September 1, 1998 JB (Age 43, Florida, USA) What does Pluto consist of chemically? We don't know for sure what Pluto is made of, but its density indicates that it is about 70% rock and 30% ice. The atmosphere, which is frozen most of the time, is probably mostly nitrogen, with some methane and carbon monoxide.
April 30, 1998 Wayne (age 8, Texas, U.S.A.) How long would it take to get to Pluto? A long time! The Pluto Express, which is set to be launched in 2001, is predicted to take 5-7 years to reach Pluto. And this pair of spacecraft is relatively small and fast!
April 17, 1998 Clay (age 14, Illinois, U.S.A.) If the Milky Way is a spiral galaxy why does Pluto have an odd orbit? The Milky Way has nothing to do with Pluto's orbit. Pluto revolves around the Sun (our local star). Pluto has an odd orbit because it is not one of the original planets in the solar system. It was 'caught' by the Sun's gravity some time later.
Pluto's orbit is very uncircular and at an odd angle to the Sun's equator. This tells us it was caught by the Sun and probably was an asteroid for some time.
April 17, 1998 Beth (age 15, Florida, U.S.A.) A day on Mercury is 176 Earth days, and a year on Mercury is 88 Earth days. How is a that??? The reason is simply that Mercury sloooowwwwlllyyyy turns. Over the time Mercury has been around the Sun, it has evolved into this rhythm with the Sun.
Another example sort-of like this is Pluto orbits the Sun EXACTLY 2 times for every 3 times Neptune does. They have reached a 'harmony' of orbits.
What happens in bad harmonies? Prometheus, a Saturn moon in between 2 rings, found out the hard way. It is now in a different orbit than it was a few years ago. Prometheus got too close to the ring material and the collision moved the moon to an orbit 19 degrees off its orbit from before.
February 27, 1998 Alexandra (age 15, Camp Grove) How big is Pluto actually? Like give an example. Pluto is 2,300 km in diameter. This is about two-thirds the diameter of our moon, or half the width of Mercury.
December 31, 1997 Rebecca (age 10, Texas, USA) What is Pluto's rotational speed? The rotational speed of Pluto is approximately 47 km/hr.
December 31, 1997 David (age 25, Canada) Is Pluto a planet or not? Historically, Pluto has been considered a planet. A planet is defined by three properties.
1) It must be orbiting a star.
2)It must not be a star or star-like object.
3)Its self-gravity must be enough to hold it in the general shape of a sphere.
December 30, 1997 Christie (age 13, Corvallis, USA) How hot is Pluto? Mars? Mercury? Pluto:-229o C
Mars:-82o C to 0o C
Mercury:-184o C to 427o C
This information is available for every planet on each planet's Planetary Facts page.


Last modified October 14, 2003 by Jennifer Bergman.

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