Pluto

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Pluto
Diameter 0.18DE Rotation Period 6 days 9
hours Orbital Period 250 years Distance
from Sun 39.44AU Orbit Eccentricity
0.25 Tilt 118
degrees Temperature possibly 228C to
-238C Atmosphere probably N, CO and methane
when not frozen Gravity 0.069g Moons 1 Visits n
one
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Pluto and Charon
Pluto's eccentric orbit intersects Neptune's
orbit, so sometimes is closer to the sun than
Neptune Pluto has an atmosphere when it is close
to the sun, which then freezes as the planet
moves away from the sun Charon discovered in 1978
(diameter 1200 km, about half the size of Pluto)
Pluto is in a 32 orbit resonance with Neptune
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The Outer Solar System The Kuiper belt
An asteroid belt beyond the orbit of Neptune
between 30-100 AU, consisting of icey bodies more
like comets than asteroids
Also the Centaur group (Chiron etc) of asteroids
that lie beyond the orbit of Saturn may also be
Kuiper belt objects
Red Orbits Plutinos Blue Orbits Classical
Kuiper Belt Objects Black Orbits SKBOs
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Quaoar The Largest Kuiper Belt Object
Discovered June 4 2002, by Michael Brown and
Chadwick Trujillo
(California Institute of Technology)
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Comets
Comets are essentially dirty lumps of ice that
melt as their highly eccentric orbits take them
closer to the sun.
The melting process creates geysers of carbon
dioxide and water vapour that forms a kind of
atmosphere called a coma around the comet's
nucleus
Two tails trail beyond the comet in its orbit
one tail consists of dust and points away from
the comet's direction of motion the other tail
consists of ionised plasma that points away from
the sun
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The Giotto probe
Launched in 1985 by ESA to study Comet Halley on
its last close encounter with Earth (next time
will be 2061)
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(above) Nucleus of Comet Wild 2 as observed by
the Stardust probe (right) Nucleus of Comet
Halley as observed by the Giotto probe
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There are two types of Comets
Long period comets have aphelia of 50,000 AU and
are thought to originate in the theorised Oort
Cloud of comets they have only ever been
observed once (e.g. Hyakutake). High and random
orbital inclinations suggest the Oort cloud is a
large shell rather than a disc.
Periodic comets reach perihelion roughly every
100 years, and are thought to originate in the
Kuiper belt disc (e.g. Halle-Bopp, Halley's Comet)
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Meteor Showers
Meteor showers are regular annual events caused
by the Earth passes through a patch of its orbit
where a periodic comet has left behind a dust
trail These dust particles burn up in the
Earth's atmosphere leaving behind bright trails
that light up the sky
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All meteor trails in the sky appear to originate
from a single radiant.
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The largest meteoroids will survive the passage
through the Earth's atmosphere and land on the
surface as a meteorite. Like asteroids, some
meteorites are Iron based, others are just rocks