What is Pluto: Definition and 68 Discussions

Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first and the largest Kuiper belt object to be discovered.
After Pluto was discovered in 1930, it was declared to be the ninth planet from the Sun. Beginning in the 1990s, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt and the scattered disc, including the dwarf planet Eris. This led the International Astronomical Union (IAU) in 2006 to formally define the term "planet"—excluding Pluto and reclassifying it as a dwarf planet.
Pluto is the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU (4.4–7.4 billion km) from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding. Light from the Sun takes 5.5 hours to reach Pluto at its average distance (39.5 AU).
Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra. Pluto and Charon are sometimes considered a binary system because the barycenter of their orbits does not lie within either body.
The New Horizons spacecraft performed a flyby of Pluto on July 14, 2015, becoming the first and, to date, only spacecraft to do so. During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons. In September 2016, astronomers announced that the reddish-brown cap of the north pole of Charon is composed of tholins, organic macromolecules that may be ingredients for the emergence of life, and produced from methane, nitrogen and other gases released from the atmosphere of Pluto and transferred 19,000 km (12,000 mi) to the orbiting moon.

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  1. Cerenkov

    B Questions about Lagrange points in the Pluto / Charon system

    Hello. With the recent interest in the JWST orbiting at the L2 Lagrange point of the Earth - Moon system, I was wondering about the dynamics of the Pluto - Charon system. Specifically, the barycentre of that system. This barycentre lies at a point in space between these two bodies. Does...
  2. Michal Fishkin

    How to install PLUTO on Windows

    Hi! I'm a first-year engineering student. I'm working on a project and was having trouble getting some of the software. I was hoping someone in this forum knew what I was dealing with and could help me out. I would really appreciate it. :) The code is called PLUTO. It's found here...
  3. J

    Kepler's 3rd Law Question finding how long a year is for Pluto

    Homework Statement Kepler's Constant for any object or planet orbiting the sun is 3.36x1018m3/s2. Calculate how long a year is for Pluto given the "radius of object" is 3.0x106m and the "mean radius of orbit" is 5.9x1012 Answer: 7.82x109s Homework Equations K = T2/R3 The Attempt at a...
  4. Y

    Calculating Projectile Distance on Pluto

    Homework Statement An astronaut throws a rock at 12 m/s at an angle of 25° above horizontal from a height of 3.25 m above the surface. How far horizontally does the rock travel before hitting the surface of Pluto? Pluto has a mass of 1.27 E22 kg And a radius of 1.14E6 m Homework Equations...
  5. C

    B Ring Found Around Pluto Neighbor Haumea

    A ring has been found around Haumea, a world more than 2 billion kilometres beyond Pluto. The ring is the most distant ever seen in our solar system. Read more at New Scientist .
  6. wolram

    B What do you think of the new names for features on Pluto

  7. Andy Resnick

    Stargazing Did I Capture Pluto in My Backyard?

    Two images, taken on 7/25 and 7/27, both at 11pm. Couldn't use my equitorial mount- a house was in the way- these are stacks of 0.8s exposures (400/2.8, ISO 2500) and heavily post-processed. Pluto's a planet, I don't care what anyone else says. :)
  8. John Dalton

    B What is the atmospheric pressure on Pluto and how can it sustain gases?

    The New Horizon reached Pluto in April of previous year. It shown that Pluto's surface contains mixtures of various gases , such as CH4 and gaseous H2SO4. Now , the query of mine is that- Pluto is situated very far from Sun and is very cold. Please someone justify me how can this gases be...
  9. S

    Why is it that Mercury rotates at a faster rate than say Pluto

    If dark matter is responsible for the inner stars within a galaxy rotating at the same rate as the outer stars, then why is it that murcury rotates at a faster rate than say pluto.This posses the question why are we searching for evidence of dark matter deep in the Earth when there seems to be...
  10. W

    Stargazing [just for fun] Planet Definition

    So I'm reading in the news and a group of scientists from the New Horizons missions appear to be reopening "The Pluto Debate" with yet another new definition of planet at the Lunar and Planetary Science Conference in March:rolleyes:. If accepted their definition of planet would increase the...
  11. grandpa2390

    Stargazing The Sun from Pluto: Visibility & Brightness

    This has always been something that has interested me. 2 things that I have found from the internet is that 1.) The Sun viewed from Pluto is (150 or 250) times brighter than the full moon. It varies of course depending on where Pluto is in its orbit. 2.) The Sun is about 30 arcminutes viewed...
  12. E

    Calculating Luminosity and Temperature of the Sun from Pluto

    Hey all, I think that I'm doing this problem correctly but I'm getting an answer that's a couple thousand Kelvins off. Sorry if I should have posted this in the "advanced" section. 1. Homework Statement Part of a flat region of Pluto has the Sun directly overhead. Its surface temperature is 58...
  13. P

    NASA New Pluto images from NASA's New Horizons

    New Pluto images from NASA's New Horizons New close-up images of Pluto from NASA's New Horizons spacecraft reveal a bewildering variety of surface features that have scientists reeling because of their range and complexity. Continue reading...
  14. Greg Bernhardt

    Insights Think You Know Pluto? - Comments

    Greg Bernhardt submitted a new PF Insights post Think You Know Pluto? Continue reading the Original PF Insights Post.
  15. Saleh0003

    Why does Pluto revolve clockwise

    Why the pluto have opposite revolving direction (clockwise) opposite to all other planets of our solar system?
  16. 1977ub

    Guidelines for including "atmosphere" in a body's "diameter"

    When we see an official description of Pluto's "diameter" it is given without the atmosphere. The official diameters of the gas giants seem to include many layers of gaseous atmosphere. Is this difference merely a convention? Or is there a good reason for treating e.g. Pluto differently than...
  17. R

    Can Beamed Propulsion be a Viable Method to Reach Pluto?

    The New Horizons results on Pluto are tantalizing. I was trying to come up with methods to get an orbiter or lander there. The problem is at a 31 AU distance from Earth solar power would only be 1/1000th as strong. However, with parabolic mirrors or Fresnel lenses we could focus a large amount...
  18. C

    Is Pluto Really Bigger Than Eris? New Horizons Settles the Debate.

    New Horizons has found that Pluto is larger than its greatest rival, Eris. Last year, other observations suggested that Pluto was around 1,471 miles across, which would have meant it was bigger than Eris, whose diameter is 1,445 miles. Link: Pluto Regains Its Title as the Largest Object in Its...
  19. R

    New Horizons flyby of Pluto [updated for Ultima Thule]

    Into July. Now only two weeks to wait for the real thing ... ! http://www.nasa.gov/mission_pages/newhorizons/main/index.html
  20. tony873004

    Simulation of New Horizons arrival day at Pluto

    Pluto, Charon, Hydra, Nix, Kerberos and Styx rapidly grow larger as New Horizons approaches, and then passes through the system. It then proceeds to pass through the umbra shadows of both Pluto and Charon so scientists can study their atmospheres. In this simulation, you can control the speed...
  21. Drakkith

    New Horizons Sees First Features on Pluto

    From here: http://www.slate.com/blogs/bad_astronomy/2015/04/29/pluto_new_horizons_sees_surface_features_for_the_first_time.html "At a press conference on Wednesday astronomers working on the New Horizons space probe revealed new images that show surface features on Pluto for the first time!"
  22. diogenesNY

    Coloured Pluto comes into view

    As reported by the BBC: By Jonathan Amos BBC Science Correspondent The New Horizons probe, which is bearing down on Pluto, has captured its first colour image of the distant dwarf planet. The picture, just released by the US space agency, shows a reddish world accompanied by its biggest moon...
  23. M

    Chance for the public to name features on Pluto and Charon

    There is a public campaign to submit names for the features on Pluto and Charon. This opportunity ends on April 24, 2015. I have already nominated Leonard Nimoy since Pluto is the god of the underworld and Charon carries the souls of the newly deceased across the river Styx to the afterlife I...
  24. M

    NASA New Horizons NASA's mission to pluto

    For anyone interested in the New Horizons Pluto encounter you can view it's progress here: http://pluto.jhuapl.edu/
  25. BobG

    Exploring Pluto & Charon w/ New Horizons: A Reflection

    The New Horizons space probe is getting close enough to get some interesting pictures of Pluto and Charon, including this little animation that illustrates how Pluto and Charon orbit around their combined center of mass. I find this amazing. When I was born, no one had ever launched an...
  26. F

    Pluto's Potential: Exploring the Possibility of Planetary Status

    Hi Guys! Is there any chance for Pluto to clean up it's orbit and become a big boy someday? Thanks a lot.
  27. T

    Time the Earth requires to go towards Pluto?

    Homework Statement Suppose that, suddendly, the gravitational attraction between the Earht and the Sun goes away. How many time will the Earth require to reach an orbital distance from the Sun equal to the actual orbital radius of Pluto? (Sun-Earth: 150*10^6 km; Sun-Pluto: 5900*10^6 km...
  28. |Glitch|

    Is Pluto a Collisional Family? Examining its Unique Orbit and Recent Moons

    I realize that some people may still be sensitive concerning Pluto's declassification as a "planet" by the IAU. However, what the IAU did not do was establish exactly what Pluto is. As a result, Pluto is now considered a "Trans-Neptunian Object", a "Kuiper Belt Object", a "Plutoid", a "Dwarf...
  29. C

    Pluto Regains Its Title as Largest Object in the Edgeworth-Kuiper Belt

    Rejoice, Pluto fans! Distant world surpasses its rival, Eris, in new analysis. Link: ScienceNOW
  30. S

    Determining the mass of Pluto using its moon

    Homework Statement On June 22, 1978, James Christy made the first observation of a moon orbiting Pluto. Until then, the mass of Pluto was not known, but with the discover of its moon, Charon, its mass could be calculated with some accuracy. Explain. 2. The attempt at a solution "By...
  31. T

    After Pluto what are new horizons plans?

    I know that they planned on going to Pluto then another Kuiper belt object, but have they found another besides Pluto? And what are they going to do after that, are they going to shoot for space like the voyager spacecraft ?
  32. W

    Just how dark is Pluto from orbit? How about Saturn?

    Quick question that maybe someone here could answer. I could probably dig up a bunch of math equations and answer it too, but I'm guessing someone here already has a good idea about the answer. Placing the Sun at the center of a sphere whose radius is equal to the distance of the Sun to...
  33. G

    Calculating Pluto's Orbital Time Above/Below Ecliptic

    I'm trying to determine the length of time Pluto spends above/below the ecliptic. I've got these figures: semi-major axis: 39.264 AU semi-minor axis: 34.031 AU orbital eccentricity: 0.249 approx orbital circumference: 230.85 AU orbital inclination is 17.142° (I'm thinking this number...
  34. D

    What would it take to terraform Pluto and Charon?

    As in the title What would it take to terraform Pluto and Charon? besides LOTS of money... is that possible?...
  35. F

    Infer diameter of Pluto from orbiting Charon

    Homework Statement Imagine viewing an eclipse of Charon by Pluto. Assume the satellite orbit is nearly circular, of known radius a, and is viewed edge-on. Explain how you could use the observations to infer a diameter for Pluto Homework Equations Orbital radius R=a The Attempt at a...
  36. Philosophaie

    Will Pluto crash into Neptune?

    The orbit of Pluto crosses the orbit of Neptune because the eccentricity of Pluto is much greater than Neptune and the rest of the Planets. This causes Pluto to stray into the path of the orbital plane of Neptune. Using a present day model to calculate a happenning of more than 100 years is a...
  37. Drakkith

    What Are the Latest Discoveries About Pluto's Moons?

    Just saw this article here about it being announced on 20 July of this year, 2011! http://en.wikipedia.org/wiki/S/2011_P_1
  38. B

    Is Tyche the Missing Planet in Our Solar System?

    http://www.nationalpost.com/m/blog.html?b=news.nationalpost.com/2011/02/15/new-giant-planet-may-repeat-may-be-discovered-in-our-solar-system&s=Opinion http://www.independent.co.uk/news/science/up-telescope-search-begins-for-giant-new-planet-2213119.html Any comments on the planet...
  39. P

    Could Pluto support an atmosphere of methane?

    Homework Statement Pluto is believed to have a radius of 1500 km, a mass of 1.5x10^22 kg, and a surface temperature of 55 K. Could Pluto support an atmosphere of methane, CH4? Homework Equations The Attempt at a Solution First some information: The problem is from a book...
  40. D

    Pluto not longer being a planet.

    What do you think about the decision?
  41. L

    Is There a Planetoid Bigger Than Pluto?

    I wonder is there a planetoid bigger than pluto in the solar system or is it possible that there could be a planet that orbits the sun but is to remote to see.
  42. L

    Stargazing Oops, I didn't read the post good enough, sorry!Last edited: Oct 30, 2016

    I have a question that I could really use some help mathematically on. At its closest to Earth, Pluto is 28.6 AU from Earth. Can the Hubble Space Telescope distringuish any features on Pluto? Justify your answers using calculations. Please help! I know that the diameter of Pluto is...
  43. P

    Unraveling the Mystery of Planetary Motion: Mercury & Pluto

    why does mercury move with such velocity while pluto is much slower?
  44. J

    What Causes Pluto's Elliptical Orbit Around the Sun?

    I understand that planets orbit follows a curve in spacetime created by the sun. Most of the planets follow the curve with seemingly a consistent radius. However Pluto follows an ellipse around the sun an appears to be inconsistent with the curve in spacetime created by the sun. Apologies if...
  45. S

    How Fast Does a Spaceship Travel from Earth to Pluto and Back in 11 Hours?

    Homework Statement A spaceship leaves earth, travels to Pluto (which os 5 hours of distance away at the time), and then returns to Earth in exactyly 11 hours later. assume the spaceships acceleration time is very short so it is always traveling at a constant speed. also assume that Earth and...
  46. Loren Booda

    Exploring the Twinkling Phenomenon of Pluto and Planets

    Stars twinkle because our atmosphere's turbulence causes these point-like bodies to scintillate, whereas planets supposedly appear large enough not to twinkle. Is Pluto (a distant and small planetoid) enough of a point to twinkle as seen from Earth?
  47. U

    Twin 1 goes on a rocket flys to pluto at .99c

    I have questions: 1) twin 1 goes on a rocket flys to pluto at .99c and comes back to Earth (all uniform motion, somehow). When he gets back he sees twin 2 is older. But since twin 2 was moving away from him at .99c why doesn't twin 2 see him as older? 2) Why does something gain mass as it...
  48. P

    Could ever Pluto slam into Neptune?

    Pluto's orbit intersects with Neptune's, so that may happen one day?
  49. P

    Pluto belongs to a new category : plutoids

    After only two years of being a dwaf planet, Pluto now belongs to a new category: http://www.space.com/scienceastronomy/080612-pluto-planet.html Correction: "#comments" removed
  50. R

    Pluto & Charon's Center of Mass - 6871.5 km

    Homework Statement Pluto's diameter is approximately 2370 km, and the diameter of its satellite Charon is 1250 km Although the distance varies, they are often about 1.99×104 km apart, center-to-center. Assuming that both Pluto and Charon have the same composition and hence the same average...