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Pluto
A Dwarf Planet
General Facts About Pluto
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Pluto orbits beyond the
orbit of Neptune (usually)
It is much smaller than any
of the official planets and
now classified as a "dwarf
planet“
In Roman mythology, Pluto
(Greek: Hades) is the god
of the underworld
Pluto was discovered in
1930 by a fortunate
accident
we now know that there
are a very large number of
small objects in the Kuiper
Belt beyond the orbit of
Neptune, some roughly
the same size as Pluto
More General Facts About Pluto
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Pluto has a satellite, Charon.
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Charon was discovered in 1978
In late 2005, two additional tiny moons were found to orbit Pluto (known
as Nix and Hydra). They are estimated to be between 60 and 200 km in
diameter
Pluto's orbit is highly eccentric. At times it is closer to the Sun than
Neptune (as it was from January 1979 thru February 11 1999)
Pluto rotates in the opposite direction from most of the other planets
Pluto's equator is at almost right angles to the plane of its orbit
Comparison of Earth and Pluto
Earth
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orbit: 149,597,871 km (1
AU) from the Sun (average)
diameter: 12,713 km
mass: 5.9736 x 1024 kg
Revolution: 365.25 days
Rotation: 24 hours
Rotational axis: tipped 23.5
degrees
Pluto
 orbit: 5,913,520,000 km (39.5
AU) from the Sun (average)
 diameter: 2274 km
 mass: 0.0125 x 1024 kg
 Revolution: 247.7 Earth years
 Rotation: 6.387 days
 Rotational axis: tipped 122
degrees
Comparison of Earth and Pluto
Pluto is
smaller than
seven of the
solar
system's
moons (the
Moon, Io,
Europa,
Ganymede,
Calistoga,
Titan and
Triton)
Missions to Pluto
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Pluto has not yet been visited by a spacecraft
Even the Hubble Space Telescope can
resolve only the largest features on its
surface
A spacecraft called New Horizons was
launched in January 2006. If all goes well it
should reach Pluto in 2015
New Horizons Mission
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Since Pluto is so far from Earth, little was
known about the dwarf planet's size or
surface conditions until 2015, when NASA's
New Horizons space probe made a close
flyby of Pluto.
New Horizons Mission
What did New Horizons find?
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Pluto has a diameter of 1,473 miles (2,370 km)
A variety of surface features, including mountains that
reach as high as 11,000 feet (3,500 meters), comparable to
the Rocky Mountains on Earth.
Pluto's surface is also covered in an abundance of methane
ice (New Horizons scientists observed significant
differences in the way the ice reflects light across the dwarf
planet's surface.)
a large heart-shaped region known unofficially as
Tombaugh Reggio (after Clyde Tombaugh)
New Horizon Photos of Pluto
Why Is It No Longer Considered a Planet?
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Due to additional
objects being
discovered including
Eris (a dwarf planet in
the Kuiper Belt) which is
27% more massive than
Pluto, the IAU
(International
Astronomical Union)
reclassified Pluto and
the other objects as
dwarf planets
Kuiper Belt objects are
comet-like in
composition