Ch12.pdf - Dr. Morales Astronomy M01 Introductory Astronomy...

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Astronomy M01
Introductory Astronomy
By Dr. Morales
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• Ring and Moon Systems Introduced
• The Galilean Moons of Jupiter
• Titan and Triton
• Pluto and Charon
• Planetary Rings
Ch. 12: Rings, Moons & Pluto
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Solar System Moons
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Moons of the outer solar
system are not composed of
the same materials as the
mostly rocky objects in the
inner solar system.
Icy moons formed in regions
of lower temperature.
Most of these objects also
contain dark, organic
compounds mixed with their
ice and rock.
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Largest Moons, Smallest Planets
• Moons are held in place by gravity around of their parent planets
• They are @ the exact distance necessary to orbit—too close, they would be pulled into the
planet; too far, they would drift out of orbit & into space
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Jupiter’s Moons
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Jovian Moons
• Jupiter has 79 natural satellites (moons)
• The 4 largest: Io, Europa, Ganymede, & Callisto
• Their orbits form a pattern known as a Laplace resonance —for every 4 orbits Io makes around
Jupiter, Europa makes exactly 2 & Ganymede makes exactly 1
• gravitationally distorting their orbits into elliptical shapes (each receives an extra tug from its neighbors at the
same point in every orbit)
• The tidal force from Jupiter, however, works to circularize it
• Results in regular tidal flexing à heats their interiors by friction
• Seen dramatically in the extraordinary volcanic activity of innermost Io (subject to the strongest
tidal forces), and to a lesser degree in the geological youth of Europa's surface (indicating recent
resurfacing of the moon's exterior)
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What would life on Europa look like?