The Solar System: An Insider’s Guide Thursday! The Gas Giants,… and one more!

Review of Terrestrial Planets They were fairly close to the Sun, and to each other, They were all fairly similar in size They were all fairly similar in their composition, specifically the amt of rock versus gas, overall density, etc.

Beyond Mars... An asteriod belt, but we’ll get back to this on Friday Incredibly large, very gaseous objects: –Jupiter: known to ancients, important to Galileo –Saturn: known to ancients, large, bright rings –Uranus: –Neptune: discovery due to physics—gravity Then there’s Pluto: small, rocky, eccentric

Jupiter Overview This is a page from Galileo’s observing log on the planet Jupiter. Just as he’d done with Venus, Galileo became the first witness to a dynamic spectacle around this large gas giant. He observed four tiny points of light, now known as the Galilean satellites, which moved around Jupiter (and not around the Earth). Moreover, their periods and distances from Jupiter followed Kepler’s laws!

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Saturn Overview Titan probed by Cassini

More on Saturn

Uranus Overview Why doesn't Uranus radiate more heat than it receives from the Sun as the other gas planets do? Is its interior cold? Why is its axis so unusually tilted? Was it due to a massive collision? Why do Uranus and Neptune have so much less hydrogen and helium than Jupiter and Saturn? Is it simply because they are smaller? or because they're farther from the Sun? What will happen to Uranus's weather as it progresses thru its seasons?

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Neptune Overview Neptune is composed mostly of ice, hydrogen and helium. It may have a small, rocky core, and an icy mantle that blends into the atmosphere. Neptune radiates almost three times as much heat energy as it gets from the distant Sun. Some of this excess heat is probably left over from the formation of this planet and some is generated by the slow collapse of the surface because of the planet's own gravitational forces.

Pluto Overview Pluto is the farthest planet from the Sun (usually) and by far the smallest. Pluto is smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton). There is mounting debate on whether it is a true planet. FOOTNOTE: After the discovery of Pluto, it was quickly determined that Pluto was too small to account for the discrepancies in the orbits of the other planets. The search for Planet X continued but nothing was found. Nor is it likely that it ever will be: the discrepancies vanish if the mass of Neptune determined from the Voyager 2 encounter with Neptune is used. There is no evidence for a tenth planet based solely on Neptune’s mass. Like Earth, Pluto has only one moon, Charon. It is half the size of Pluto! Pluto and Charon are closer in size than any other planet-moon system in our solar system, and are sometimes called a double planet.

More on Pluto HST Image! The least understood planet. Even HST can barely resolve it. Its Moon was undiscovered until It’s size, peculiar orbit, and unusual composition pose many questions. It is the only unexplored SS object.

Outer Planets all together now.