SOLAR SYSTEMS CHAPTER 21

definition Objects that revolve around a star Major members Planets Moons Minor members Dwarf planets Asteroids Comets meteoroids

What is a planet? (as of Aug. 2006) The IAU said that the definition for a planet is now officially known as "a celestial body that (a) is in orbit around a star (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a (nearly round) shape and (c) has cleared the neighborhood around its orbit." (not in a swarm of rocks)

Our solar system scoreboard Planets= 8 Moons= 167 Dwarf planets= 5 Asteroids= 536,000+ Comets= 3,062

Exosolarsystems Other solar systems 565 new solar systems confirmed! Over 687 planets (exoplanets) First discovered in 1995 Estimated over 50 BILLION

Earth like planets (habitable zone) Maybe 2? Gliese D 6x more massive than earth “superearth” In Libra 20 lya HD 85512 b In Vela 26 lya

METHODS to find a new planet http://planetquest.jpl.nasa.gov/Planet_Finder/planetfinder.html

Radial Velocity Planets are detected by studying light shifts due to star wobbles Uses Doppler Effect Red light moves towards Blue light moves away

Astrometry Measures star wobbles from geometry

Transit method Planet blocks star (eclipse) Light from star is lessen Kepler mission

Optical detection Block star’s light out using a chronograph

List of exoplanets http://planetquest.jpl.nasa.gov/atlas/atlas_search.cfm

Exoplanet missions Kepler- launched 2009 Has found 7 planets so far

Other research LBT (large binocular telescope) Keck telescopes (Hawaii) Spitzer Space Telescope Infrared telescope

Our Solar System

Our solar system

The planets drawn to scale

INNER PLANETS

INNER PLANETS Terrestrial Rocky No rings Smaller compared to Outer planets

MERCURY No atmosphere Temperatures fluctuate wildly MESSANGER is currently orbiting Mercury- has completed 282 orbits (so far!)

Sept. 29, 2009 MESSANGER

Messenger 9/21/11 Mapping surface of Mercury

VENUS THICK atmosphere Rotation is retrograde Hot! Crushing pressure Sun rise in west; set in east

Pancake volcanoes

MARS Thin atm. Windy Surface similar to Earth Volcanoes Old river valleys- where’s the water? Best chance to find fossil (life?) in SS

Opportunity and Spirit http://marsrovers.jpl.nasa.gov/home/

Mars Moons Phobos Deimos

Jovian Planets Outer planets Large Many moons all have rings Made of gas

JUPITER Often captures comets/asteroids Shoemaker/Levy comet (1994)

Jupiter’s Ring system Feb. 2007

Jupiter’s New Moons Jupiter now has 63 known moons 23 moons were discovered in 2002-3 by Earth-based telescopes http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Moons

Saturn’s Rings Made of Water ice and dust Sheppard moons keep rings in place

Uranian Weirdness

A few of Uranus’s moons MIRANDA PUCK ARIEL OBERON

Neptune Very active weather

Triton- Liquid nitrogen volcanoes Cantaloupe terrain Underground oceans? Alien life?

Planet ? 2003 UB313 Renamed Eris (Xena)

What is a planet? (as of Aug. 2006) The IAU said that the definition for a planet is now officially known as "a celestial body that (a) is in orbit around a star (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a (nearly round) shape and (c) has cleared the neighborhood around its orbit." (not in a swarm of rocks)

Pluto Dwarf planet

Lowell Observatory where Pluto was discovered 1939

Plutoids Dwarf planets beyond Neptune Established in 2008

Planets, dwarf planets, plutoids

How many moons does Pluto have?

We’re on the way… New Horizons spacecraft was launched in Jan. 2006 Will arrive at Pluto July 2015