Not Your Parents’ Solar System!

Not Your Parents’ Solar System!

Frank SummersSpace Telescope Science

InstituteNSTA Institute Symposium

November 15, 2003

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

MercuryVenus

EarthMars

JupiterSaturn

UranusNeptune Pluto

MyVery

Energetic Mother

JustServed

UsNine

Pizzas

What’s wrong?What’s wrong?

• Memorization• Factoids• Highlights differences• Little or no relevance• Little or no “big picture”

An ImprovementAn Improvement

• Compare and contrast– Discuss broad ideas– Apply to planets, moons, etc., as a

group

• Highlight similarities– Appearance– Characteristics– Events

Other comparisonsOther 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 ContrastCompare and Contrast

• Messages– What happens on Earth happens

elsewhere– Solar system is understandable

• Problems– Need to establish facts before

comparison– Big picture still lacking

21st Century View21st 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 BeltScientific View of the Asteroid Belt

500 million miles500 million miles

Thousands of Thousands of asteroids …asteroids …

about a million about a million miles apart!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 SystemFamilies of the Solar System• Classes of similar objects

– Size– Composition– Orbit size– Orbit shape– Orbit inclination– Moons– Rings

Families of the Solar SystemFamilies 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?What about Pluto?

• Not a rocky planet• Not a gas giant planet

• For teachers, it is an opportunity

Planet PlutoPlanet Pluto

• 1930 Tombaugh discovers Pluto

Double Take: CharonDouble 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/CharonFirst Pictures of Pluto/Charon• 1995 – Hubble Space Telescope

infrared• 1996 – Hubble Space Telescope

visible

First Pictures of PlutoFirst Pictures of Pluto

Black Sheep of the PlanetsBlack Sheep of the Planets

• Pluto is the oddball– Size– Companion– Composition– Orbit– 3:2 resonance with Neptune

• Pluto/Charon as double ice planet?

Kuiper BeltKuiper 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

KBOsKBOs

• 1992 – Jewitt & Luu find object dubbed QB1

• Distance of 42 AU• First (third?) object

discovered in the Kuiper Belt

More and more KBOsMore 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 30-50 AU• Plutinos – Neptune resonance• Scattered – Neptune affects orbit• Classsical – Separated from Neptune

Pluto/Charon orbits within Kuiper Belt

Large KBOsLarge KBOs

• Pluto still larger, but not by that much

• Note: plot below doesn’t include Quaoar

Binary KBOsBinary KBOs

• Pluto/Charon not the only binary object

• Nine discovered so far (Nov 2003)• All types of KBOs have binaries

What is Pluto?What is Pluto?

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

Kuiper Belt Expert’s ViewKuiper 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 PositionIAU 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?What is a Planet?

• Solar system alone is category of one

• What about other solar systems?

Beta Pictoris

Disks around Other StarsDisks around Other Stars

• Lots of them• Proplyds – proto-planetary disks• Kuiper Belt sized and larger• Some substructure seen

Planets around Other StarsPlanets 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 StarsPlanets 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 StarsPlanets 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 SystemPerspective 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