Transcript Satellite names worth remembering

Ast 1001, 17 Oct 2007
Ast 1001, 17 Oct 2007
MOONS (= SATELLITES)
of the Gas Giant Planets
Ast 1001, 17 Oct 2007
JUPITER: Numerous satellites...
Discovered by Galileo, 1610:
Io (a.k.a. “J I”)
Europa (J II)
Ganymede (J III)
Callisto (J IV)
For almost 300 years, they were the
only known Jovian satellites (“Jovian”
means belonging to Jupiter).
Ast 1001, 17 Oct 2007
Ast 1001, 17 Oct 2007
Jupiter and the orbits of
Io
Europa
Ganymede
Callisto
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(Digression)
Ole Roemer, Jupiter’s moons, and
the speed of light, 1675
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Earth – Jupiter distance
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Io
Europa
Ganymede
Callisto
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Likely interior of Ganymede (theoretical?)
ice-covered surface
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JUPITER: At least 57 known satellites
In 1892, E. Barnard discovered
Amalthea (J V) -- a small captured
asteroid inside the orbit of Io.
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Orbit of Amalthea (J V)
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Amalthea: about 200 km across
( same size as a large asteroid )
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... Then came
Himalia (J VI, 1904),
Elara (J VII, 1905),
Pasipha (J VIII, 1908),
and others -- 14 by 1979. Probably
all captured asteroids, relatively small.
Then the first spacecraft reached Jupiter and
began to find lots more.
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(Jupiter’s moons, continued)
A random selection:
Erinome (J XXV),
Thyone (J XXIX),
Hegemone (J XXXIX),
Karpo (J XLIV),
etc. etc. The names don’t really matter.
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Orbits of some of the “other” moons
of Jupiter (some are retrograde)
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Saturn has a mob of satellites too.
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TITAN (the big one); plus
IAPETUS, RHEA, DIONE, TETHYS, etc.
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Dione and Tethys -- icy surfaces
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Mimas -- about 400 km across
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TITAN IS DIFFERENT.
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TITAN IS DIFFERENT.
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1943 spectrum of Titan:
Methane. It has an atmosphere!
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But Titan has low gravity.
How can it hold an atmosphere??
Ast 1001, 17 Oct 2007
But Titan has low gravity.
How can it hold an atmosphere??
Answer: It’s cold:
94 ° K = -290 ° F.
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“Saturn as seen from Titan” (1944 painting)
blue sky!
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Spacecraft view of TITAN.
-- Methane and ethane clouds --
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Titan’s atmosphere is mostly nitrogen ( N2 )
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Titan’s interior ( ? )
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Titan’s
atmosphere
and
surface
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Re. Saturn and
Titan, look up the
Cassini and Huygens
space probes (2005)
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Next planet out: Uranus.
Soon after discovering Uranus,
William Herschel found that it had
several moons ...
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Oberon
Titania
Umbriel
Ariel
Miranda
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(Uranus’ satellites)
Oberon Titania Umbriel Ariel Miranda ...
Later discovered by spacecraft:
Ophelia Rosalind Portia Juliet Rosalind
Bianca
Cordelia
Caliban Puck Prospero
-- and others. At least 27 so far.
Ast 1001, 17 Oct 2007
Ast 1001, 17 Oct 2007
Next planet: Neptune.
Big moon Triton was discovered soon after
Neptune was ... (1846)
Ast 1001, 17 Oct 2007
Next planet: Neptune.
Big moon Triton was discovered soon after
Neptune was ... (1846)
Triton moves backward – in a “retrograde
orbit.” This isn’t easy to explain, for such
a large moon.
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Spacecraft image of Triton
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Neptune also has the usual horde of smaller
satellites: Nereid, Galatea, Naiad, Proteus,
and others.
Half of them were discovered by the Voyager
2 spacecraft when it passed that planet in
1989.
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Planetary RINGS
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Narrow rings of Uranus
-- discovered in late 1970’s --
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Neptune too
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And even Jupiter!
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In general, planetary rings were probably
formed when small moons or possibly
comets approached too close to the gas
giant planets, were broken up by tidal
forces.
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In general, planetary rings were probably
formed when small moons or possibly
comets approached too close to the gas
giant planets, were broken up by tidal
forces. Saturn is an unusually dramatic
example.
Ast 1001, 17 Oct 2007
Ast 1001, 17 Oct 2007
Satellite names worth remembering
Ast 1001, 17 Oct 2007
Satellite names worth remembering
PHOBOS & DEIMOS -- asteroids captured
by Mars
Ast 1001, 17 Oct 2007
Satellite names worth remembering
PHOBOS & DEIMOS -- asteroids captured
by Mars
IO -- Jupiter’s moon heated by tidal forces
Ast 1001, 17 Oct 2007
Satellite names worth remembering
PHOBOS & DEIMOS -- asteroids captured
by Mars
IO -- Jupiter’s moon heated by tidal forces
TITAN -- Saturn’s moon with dense
atmosphere
Ast 1001, 17 Oct 2007
Satellite names worth remembering
PHOBOS & DEIMOS -- asteroids captured
by Mars
IO -- Jupiter’s moon heated by tidal forces
TITAN -- Saturn’s moon with dense
atmosphere
TRITON -- mysterious retrograde orbit
around Neptune
Ast 1001, 17 Oct 2007
Also remember:
Objects beyond Jupiter tend to be icy,
or at least they have icy outer layers.
(“ice” can mean CH4 , NH3 , H2O ,
and maybe other frozen or slushy stuff)
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We haven’t mentioned Pluto yet.
That’s not because we forgot; it turns out
that Pluto is a different, unfamiliar type
of object !
Ast 1001, 17 Oct 2007