Not Your Parents’ Solar System! Frank Summers Space Telescope Science Institute NSTA Institute Symposium November 15, 2003

How I learned the solar system Sun & 9 planets Separate section on each Mention asteroids and comets Lots of cool facts

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto My Very Energetic Mother Just Served Us Nine Pizzas

What’s wrong? Memorization Factoids Highlights differences Little or no relevance Little or no “big picture”

An Improvement Compare and contrast –Discuss broad ideas –Apply to planets, moons, etc., as a group Highlight similarities –Appearance –Characteristics –Events

Other comparisons Craters – Earth, Moon, Mercury, etc Volcanoes – Mount St. Helens, Olympus Mons, Io, etc Canyons – Grand Canyon, Mariner Valley Storms, Winds, Seasons, Weather, Ice Floes, Magnetic Fields, Moons, Rings, etc

Compare and Contrast Messages –What happens on Earth happens elsewhere –Solar system is understandable Problems –Need to establish facts before comparison –Big picture still lacking

21 st Century View Six families of the solar system –Star –Rocky planets –Asteroid belt –Gas giant planets –Kuiper belt –Oort cloud

Hollywood’s View of the Asteroid Belt

Scientific View of the Asteroid Belt 500 million miles Thousands of asteroids … about a million miles apart!

Kuiper Belt

Oort Cloud ? Billions of icy minor planets – comet nuclei Roughly spherical out to 50,000 AU Predicted by Jan Oort Explains long-period comets No observations

Families of the Solar System Classes of similar objects –Size –Composition –Orbit size –Orbit shape –Orbit inclination –Moons –Rings

Families of the Solar System Classification Structure of the solar system –Similar objects lie in similar regions Clues to solar system formation and evolution

Sun Rocky Planets Asteroid Belt Gas Giant Planets Kuiper Belt Oort Cloud

Sun Oort Cloud Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Kuiper Belt

Some Others Cheer May View Elaborate Mnemonics As Boring, Just Some Useless Nonsensical Knowledge, But

What about Pluto? Not a rocky planet Not a gas giant planet For teachers, it is an opportunity

Planet Pluto 1930 Tombaugh discovers Pluto

Double Take: Charon 1978 – James Christy (USNO) observations to refine Pluto’s orbit Notices elongated images, deduces moon 1985 – Charon occults Pluto, confirms existence Refined sizes and masses – tiny

First Pictures of Pluto/Charon 1995 – Hubble Space Telescope infrared 1996 – Hubble Space Telescope visible

First Pictures of Pluto

Black Sheep of the Planets Pluto is the oddball –Size –Companion –Composition –Orbit –3:2 resonance with Neptune Pluto/Charon as double ice planet?

Kuiper Belt History –1930 – Leonard mentions possibility of trans-Plutonian objects –1943 – Kenneth Edgeworth postulates objects beyond Pluto –1951 – Gerard Kuiper predicts that a massive Pluto would disperse small objects into a belt –1980 – Fernandez predicts belt that resembles what was eventually found

KBOs 1992 – Jewitt & Luu find object dubbed QB1 Distance of 42 AU First (third?) object discovered in the Kuiper Belt

More and more KBOs Large searches for KBOs ensued Hundreds discovered within a decade Over 600 so far (Nov 2003) Over 70,000 predicted with diameters > 100 km, orbits AU Plutinos – Neptune resonance Scattered – Neptune affects orbit Classsical – Separated from Neptune

Pluto/Charon orbits within Kuiper Belt

Large KBOs Pluto still larger, but not by that much Note: plot below doesn’t include Quaoar

Binary KBOs Pluto/Charon not the only binary object Nine discovered so far (Nov 2003) All types of KBOs have binaries

What is Pluto? You make the call –Singular ice planet –Mutant giant double comet –King of the Kuiper Belt –???

Kuiper Belt Expert’s View “So, bluntly put, one has two choices. One can either regard Pluto as the smallest, most peculiar planet moving on the most eccentric and most inclined orbit of any of the planets or one can accept that Pluto is the largest known, but otherwise completely typical, Kuiper Belt Object. The choice you make is up to you, but from the point of view of trying to understand the origin and significance of Pluto it clearly makes sense to take the second option.” Dave Jewitt, University of Hawaii

IAU Official Position IAU defines Pluto to be a planet IAU cannot define “planet” –Upper limit: not massive enough to produce any form of fusion at its core –Deuterium fusion occurs for objects about 15 times Jupiter’s mass –No lower limit specified Reasonable lower limit? –Massive enough for gravity to make it spherical –At least 13 planets –No reasonable definition produces 9 planets

What is a Planet? Solar system alone is category of one What about other solar systems?

Beta Pictoris

Disks around Other Stars Lots of them Proplyds – proto-planetary disks Kuiper Belt sized and larger Some substructure seen

Planets around Other Stars Cannot see directly (yet) Detect via gravitational pull on star –Wobble –Periodic shift of spectral lines –Monitor for many years (several orbits) –Large gas giant planets detectable

Planets around Other Stars Current count (Nov 2003) –102 planetary systems –117 planets –13 multiple planet systems At least 15% of sun-like stars have planets

Planets around Other Stars Jupiter mass planets in Mercury orbits Elliptical orbits Multiple Jupiter sized planets Saturn mass planets detected (2003) Planets around pulsars

Perspective on the Solar System Our solar system is the oddball Need to generalize our formation and evolution scenarios Implications for life in the universe –Lots of planets –Stability of orbits? New era of solar system study