Chapter 12: Rings, Moons, and Pluto

Makemake

310 year orbit Orbits in the Kuiper belt Slightly smaller than Pluto Frozen nitrogen and methane on the surface Also helped start debate on the definition of a planet

Plutos Surface

60% the size of the Moon Made of rocks and ice • Frozen methane, carbon monoxide, nitrogen Very diverse terrain

This object orbits the Sun, has no other objects in its orbit, and has no satellites/moons. It is a

A. Planet (Mercury)

This object orbits the Sun, shares its orbit with many asteroids, and has no satellites/moons. It is a

B. Dwarf planet (Ceres)

The word "planet" originally meant

B. Wanderer

Pluto

Dwarf planet ~40 AU from the Sun Orbits in 249 years Orbit is inclined 17° to the ecliptic e = 0.25

IAU also made the resolution that defined a new class of solar system objects, "dwarf planets"

Four Criteria: 1. Be in orbit around the Sun 2. Massive enough that gravity makes it nearly round 3. Has not cleared the neighborhood of its orbit 4. Not be a satellite/moon

Plutos atmosphere

Has an atmosphere at perihelion • Atmosphere freezes out at aphelion (no atmosphere) 10 degree difference • Methane and nitrogen sometimes frozen, sometimes gas

Eris

Has one known moon: Dysnomia 557 year orbit Eccentric orbit, inclined 44˚ Resides in the Kuiper belt Surface likely similar to Pluto Similar size to Pluto Instigated debate on the definition of a planet

IAU Resolution

In 2006, the International Astronomical Union created a new definition of "planet" Three Criteria: 1. Be in orbit around the Sun 2. Massive enough that gravity makes it nearly round 3. Cleared the neighborhood of its orbit

Which of the following is not true about the New Horizon's mission?

It orbited Pluto for three days to take images

Ceres

Largest object in the asteroid belt Only dwarf planet in the inner solar system First dwarf planet visited by a spacecraft (NASA's Dawn, orbiter) Made of water ice and rocky material 9 hour rotation 4.6 year orbital period 2.8 AU from the Sun

Mission to Pluto: New Horizons

Launched in 2006 Arrived at Pluto in 2015 Entire flyby sequence was one day Powered by a nuclear electric system using plutonium Used Jupiter's gravitational pull to "slingshot" out to Pluto

If you were standing on Pluto, how often would you see the satellite Charon rise each day?

Never

Plutos other satellites

Nix and Hydra • discovered in 2005 by HST Kerberos • discovered in 2011 Styx • discovered in 2012 when looking for hazards to New Horizons mission All moons likely formed from collision • Smashed material coalesced into satellites Nearly circular orbits Rotate chaotically, "tumble" • because of Pluto and Charon's orbits

Haumea

Oddly shaped One of the fastest rotating objects in the solar system • ~4 hours • Caused by a massive impact? About the same size as Pluto Orbits in the Kuiper Belt (like Eris) 285 year orbit Rocky with an icy coating Two moons: Hi'aka and Namaka

planet

Originally meant "wanderer" Stars rise and set each night, like the Sun Some of these points of light move or wander

Charon

Pluto's largest moon is Charon Charon is more than half the size of Pluto About the size of Texas Double tidal lock • Same side of Charon always faces the same side of Pluto Some craters Belt of rough terrain, almost as if something tried to pull it apart