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Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I Not exactly like Book). Uranus and Neptune : Discoveries, atmospheres, interiors, rotation, magnetic fields, moons, rings, Uranus’ axis tilt and seasons.
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Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I Not exactly like Book) Uranus and Neptune: Discoveries, atmospheres, interiors, rotation, magnetic fields, moons, rings, Uranus’ axis tilt and seasons. Pluto and Charon: Orbit, composition, other moons, why so different from Jovian planets? Transneptunian Bodies (the Kuiper belt)
Uranus and Neptune Not known to ancient greeks, discovery details. Composition : H, He, CH4, NH3,etc. Atmospheres: less active, dark spot on Neptune Interior: liquid hydrogen but no metallic hydrogen Rotation: fast (~17 hours for both) Magnetic field: strong (but not know how it is produced) Moons: many moons, Neptune’s Triton is larger than Pluto and retrograde (probably captured) Rings: dark and faint
Question 1 If Uranus is at its Autumnal Equinox, what does that mean?
Question 1 If Uranus it is at its Autumnal Equinox, what does that mean? a) Nothing, Uranus has no seasons b) The Sun is crossing Uranus’ equator from North to South c) The Sun is at its northernmost point on Uranus d) The Sun is in the southern hemisphere of Uranus
Question 2 Uranus takes 84 years to orbit the Sun. In 2007 Autumn started in the northern hemisphere of Uranus, when will Winter start in the northern hemisphere of Uranus? a) 84 years later b) 42 years later c) 21 years later d) In 2008
Larger than Pluto and in a retrograde orbit Triton: largest of Neptune’s moons
Larger than Pluto and in a retrograde orbit Why does a retrograde orbit indicate capture? Triton: largest of Neptune’s moons
Outline of Uranus, Neptune and Pluto Pluto and Charon: Orbit, composition, other moons (Nix & Hydra), why so different from Jovian planets?
Pluto and Charon Discovery of Charon with ground based telescope Hubble Space Telescope
Solar Nebula was “thinning out hence U and N are smaller than J and S and so is Pluto and its trans- neptunian relatives
Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I ) Transneptunian Bodies (the Kuiper belt): Many objects smaller than planets: similar to the asteroid belt Largest object (Eris) is slightly larger than Pluto Source of some of the comets Triton may have formed in the Kuiper belt was captured by Neptune (Triton’s orbit is retrograde)
Question 3 Would you expect the composition of objects in the Kuiper belt to be? a) The same as those in the asteroid belt b) Iron cores and silicate mantles c) Hydrogen and helium d) None of the above
Question 3 Would you expect the composition of objects in the Kuiper belt to be? a) The same as those in the asteroid belt b) Iron cores and silicate mantles c) Hydrogen and helium d) None of the above
~50 AU Sun Kuiper Belt Neptune’s Orbit
Is Pluto a planet or a Kuiper Belt object? • Pluto is well beyond Neptune, in the Kuiper Belt. • Inclined orbit is typical of Kuiper Belt objects. • Composition is typical of Kuiper Belt objects, but not like any of the other planets.
Is Pluto a planet or a Kuiper Belt comet? • One Kuiper Belt object has been found that is slightly larger Pluto’s size (Eris, a.k.a. object 2003 UB313) and several slightly smaller. • Kuiper Belt objects have similar orbital resonances with Neptune. • Kuiper Belt objects can have moons. • Triton (a captured moon of Neptune) is even larger than Pluto.
• What is Pluto like? Pluto is much smaller than any other planet, with an orbit more elliptical and more inclined to the ecliptic plane than that of any other planet. It is made mostly of ices and has a very thin atmosphere of gases that are expected to freeze onto the surface as Pluto moves farther from the Sun in its 248-year orbit. It has 3 moons. • Is Pluto a planet or a Kuiper belt object? Pluto was called a planet by the International Astronomical Union until 2006. Its properties suggest that it is one of the largest members of the Kuiper belt objects. Its composition and orbital properties match those of other Kuiper belt objects and do not fit in with the other planets. It was the largest known Kuiper belt object until summer 2005 now there is a larger one further out (Eris). What have we learned?