Outline of Uranus Neptune and Pluto Ch 8

Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I Not exactly like Book) I. Uranus and Neptune: Discoveries, atmospheres, interiors, rotation, magnetic fields, moons, rings, Uranus’ axis tilt and seasons. II. Pluto and Charon: Orbit, composition, other moons, why so different from Jovian planets? III. Transneptunian Bodies (the Kuiper belt)

Planet Distance Mass Moons Density (AU) (Earth = 1) Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune 0. 39 0. 72 1. 0 1. 5 5. 2 9. 5 19. 2 30. 1 0. 05 0. 9 1. 0 0. 11 318 95 17 17 0 0 1 2 28 18 21 8 5. 43 5. 25 5. 52 3. 95 1. 33 0. 69 1. 29 1. 64 Pluto 39. 5 0. 002 3 2. 03 (Water =1)

Uranus and Neptune n Not known to ancient greeks, discovery details. n Composition : H, He, CH 4, NH 3, etc. n Atmospheres: less active, dark spot on Neptune n n Interior: liquid hydrogen but no metallic hydrogen n Magnetic field: strong (but not know how it is produced) n Moons: many moons, Neptune’s Triton is larger than Pluto and retrograde (probably captured) n Rings: dark and faint Rotation: fast (~17 hours for both)

Interiors of Jovian Planets

Interiors

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

Triton: largest of Neptune’s moons 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?

Outline of Uranus, Neptune and Pluto II. 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

Pluto and its three Moons

Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Distance Mass (AU) (Earth = 1) 0. 39 0. 72 1. 0 1. 5 5. 2 9. 5 19. 2 30. 1 39. 5 0. 05 0. 9 1. 0 0. 11 318 95 17 17 0. 002 Moons Density (Water =1) 0 0 1 2 28 18 21 8 3 5. 43 5. 25 5. 52 3. 95 1. 33 0. 69 1. 29 1. 64 2. 03

Solar Nebula was “thinning out hence U and N are smaller than J and S and so is Pluto and its transneptunian relatives

Outline of Uranus, Neptune and Pluto (Ch. 8 part II and Ch 9 part I ) III. n n 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

Kuiper Belt ~50 AU • Sun Neptune’s Orbit

Outer Solar System

Outer Solar System

Collision in the Kuiper Belt Paiting by Daniel D. Durda

Is Pluto a planet or a Kuiper Belt object?

Is Pluto a planet or a Kuiper Belt object? n Pluto is well beyond Neptune, in the Kuiper Belt. n Inclined orbit is typical of Kuiper Belt objects. n Composition is typical of Kuiper Belt objects, but not like any of the other planets.

Is Pluto a planet or a Kuiper Belt comet? n One Kuiper Belt object has been found that is slightly larger Pluto’s size (Eris, a. k. a. object 2003 UB 313) and several slightly smaller. n Kuiper Belt objects have similar orbital resonances with Neptune. n Kuiper Belt objects can have moons. n Triton (a captured moon of Neptune) is even larger than Pluto.

What have we learned? • Is Pluto a planet or a • What is Pluto like? Kuiper belt object? Pluto is much smaller than Pluto was called a planet by the any other planet, with an International Astronomical orbit more elliptical and Union until 2006. Its properties more inclined to the suggest that it is one of the ecliptic plane than that of largest members of the Kuiper any other planet. It is belt objects. Its composition made mostly of ices and orbital properties match has a very thin those of other Kuiper belt atmosphere of gases that objects and do not fit in with are expected to freeze the other planets. It was the onto the surface as Pluto largest known Kuiper belt moves farther from the object until summer 2005 now Sun in its 248 -year orbit. there is a larger one further out It has 3 moons. (Eris).