Lecture 13: Pluto, Asteroids, and Comets

Pluto

Dwarf planet discovered in 1930, icy composition.

AU

Astronomical Unit; average distance from Earth to Sun.

Pluto's Orbit

Tilted and elliptical; resonance with Neptune.

New Horizons

NASA mission that flew by Pluto in 2015.

Pluto's Diameter

Approximately 18% that of Earth's diameter.

Charon

Largest moon of Pluto, about half its size.

Atmospheric Pressure

Pluto's pressure is ~10 microbars.

Planet Definition

Orbits a star, spherical, clears orbit neighborhood.

Dwarf Planet

Fails to clear neighborhood; includes Pluto and Eris.

Eris

Iceball discovered in 2005, more massive than Pluto.

Dysnomia

Moon of Eris, discovered alongside the planet.

Asteroids

Rocky remnants from planet formation, not round.

Ceres

Largest asteroid, diameter ~1,000 km.

Asteroid Belt

Region between Mars and Jupiter with many asteroids.

Meteorites

Solid fragments from asteroids that reach Earth.

Ice-rich Crust

Evidence found on Pluto, indicating geological activity.

Geological Activity

Pluto and Charon show significant geological changes.

Elliptical Orbit

Pluto's orbit is significantly elongated.

Inclined Orbit

Pluto's orbit is tilted relative to the solar plane.

Griffith Observatory Visit

Extra credit assignment for class participation.

JWST Discovery

Extra credit report on recent findings from JWST.

Glacial Flows

Evidence of movement on Pluto's surface.

Albedo

Reflectivity of Pluto's surface varies by region.

Nitrogen Atmosphere

Pluto's atmosphere primarily composed of nitrogen.

Rocky Planetesimals

Small rocky bodies that did not form into a planet.

Jupiter's Gravity

Influences asteroid orbits, preventing planet formation.

Meteorite

Rock from space that reaches Earth's surface intact.

Meteor

Bright tail of debris burning in Earth's atmosphere.

Meteoroid

Small body in solar system that can become a meteor.

Primitive Meteorites

Unchanged since formation 4.6 billion years ago.

Processed Meteorites

Younger meteorites that underwent differentiation or volcanism.

Comet

Icy body formed beyond the frost line in solar system.

Nucleus of Comet

Central part of a comet, often called a dirty snowball.

Coma

Atmosphere around a comet's nucleus formed by heating.

Plasma Tail

Gas escaping from coma, pushed by solar wind.

Dust Tail

Tail of a comet pushed by photons.

Oort Cloud

Region of random orbits extending to about 50,000 AU.

Kuiper Belt

Region with orderly orbits from 30-100 AU in solar system.

Meteor Showers

Caused by Earth crossing a comet's orbit.

Deep Impact Mission

Studied nucleus of Comet Tempel 1 in 2005.

Rosetta Mission

Orbited Comet 67/P for two years, deployed Philae lander.

Orbital Resonances

Gravitational interactions that disrupt asteroid orbits.

Accretion

Process of bodies merging to form larger objects.

Differentiation

Separation of materials within a body based on density.

Volcanism

Geological activity involving the eruption of molten rock.

Asteroid Composition

Primitive meteorites reveal original planetesimal characteristics.

Comet Tail Growth

Occurs when a comet nears the Sun and heats up.