The Dwarf Planet Pluto http:en.wikipedia.orgwikiPluto

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The Dwarf Planet Plutohttp//en.wikipedia.org/wik
i/Pluto

• Dr. Harold Williams
• Montgomery College Planetarium
• http//Montgomerycollege.edu/Departments/planet/

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Clyde Tombaughdiscover of Pluto
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Lowell Observatory Astrograph
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Lowell Observatory Blink Comparator
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Ganymede (Jupiter), Titan (Saturn) and Callisto
(Jupiter) Io (Jupiter), Luna (Earth), Europa
(Jupiter), Triton (Neptune) and Pluto.
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Asteroid Orbits

• Most asteroids orbit in a belt between Mars and
  Jupiter
• Trojan asteroids follow Jupiters orbit
• Orbits of near-Earth asteroids cross Earths orbit

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Wikipedia Links

• http//en.wikipedia.org/wiki/Minor_planet
• http//en.wikipedia.org/wiki/Minor_Planet_Center
• http//en.wikipedia.org/wiki/Minor_planet_number
• http//en.wikipedia.org/wiki/Eris_28dwarf_planet
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• http//en.wikipedia.org/wiki/Trans-Neptunian_objec
  t
• http//en.wikipedia.org/wiki/Asteroid
• http//en.wikipedia.org/wiki/List_of_asteroids_nam
  ed_after_important_people

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Only a tiny number of comets enter the inner
solar system - most stay far from the Sun
Oort cloud On random orbits extending to about
50,000 AU
Kuiper belt On orderly orbits from 30-100 AU in
disk of solar system
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How big can a comet be?
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Plutos Orbit

• Pluto will never hit Neptune, even though their
  orbits cross, because of 32 orbital resonance
• Neptune orbits three times during the time Pluto
  orbits twice

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Is Pluto a Planet?

• By far the smallest planet.
• Not a gas giant like other outer planets.
• Has an icy composition like a comet.
• Has a very elliptical, inclined orbit.
• Pluto has more in common with comets than with
  the eight major planets

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Other Icy Bodies

• There are many icy objects like Pluto on
  elliptical, inclined orbits beyond Neptune.
• The largest of these, Planet X was discovered
  in summer 2005, is even larger than Pluto

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Kuiper Belt Objects

• These large, icy objects have orbits similar to
  the smaller objects in the Kuiper Belt that
  become short period comets
• So are they very large comets or very small
  planets?

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What are the large objects of the Kuiper belt
like?
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HSTs view of Pluto Charon
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What is Pluto like?

• Its moon Charon is nearly as large as Pluto
  itself (probably made by a major impact)
• Pluto is very cold (40 K)
• Pluto has a thin nitrogen atmosphere that will
  refreeze onto the surface as Plutos orbit takes
  it farther from the Sun.

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Other Kuiper Belt Objects

• Most have been discovered very recently so little
  is known about them.
• NASAs New Horizons mission will study Pluto and
  a few other Kuiper Belt object in a planned
  flyby.

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Is Planet X a planet?
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Pluto and Planet X

• Plutos size was overestimated after its
  discovery in 1930
• It was considered a planet, and nothing of
  similar size was discovered for several decades
• Now other large objects have been discovered in
  Kuiper Belt, including Planet X
• Some scientists consider all of those objects
  planets others consider none of them planets.

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Sedna in Green Circlehttp//en.wikipedia.org/wiki
/90377_Sedna
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What have we learned?

• How big can a comet be?
• The Kuiper belt from which comets come contains
  objects as large as Pluto.
• What are the large objects of the Kuiper belt
  like?
• Large objects in the Kuiper belt have orbits and
  icy compositions like those of comets.
• Is Planet X a planet?
• It remains a matter of opinion because scientists
  have not yet settled on a definition of the
  minimum size of a planet.

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New Horizons Spacecraft

• http//en.wikipedia.org/wiki/New_Horizons
• Major Contractors JHU APL, SwRI
• New Horizons NASAs Pluto-Kuiper Belt Mission
  http//pluto.jhuapl.edu/

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New Horizonslaunched January 19, 2006flyby
Pluto July 14, 2015
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Spacecraft New Horizons
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Thermal Space Battery
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Antennas of New Horizons (HGA, MGA and LGA)