Not Your Parents Solar System

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Not Your Parents Solar System!

• Frank Summers
• Space Telescope Science Institute
• March 23, 2004

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How I learned the solar system

• Sun 9 planets
• Separate section on each
• Mention asteroids and comets
• Lots of cool facts

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Whats wrong?

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

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An Improvement

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

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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

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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

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21st Century View

• Six families of the solar system
• Star
• Rocky planets
• Asteroid belt
• Gas giant planets
• Kuiper belt
• Oort cloud

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Hollywoods View of the Asteroid Belt
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Thousands of asteroids about a million miles
apart!
Scientific View of the Asteroid Belt
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Kuiper Belt
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• 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 Sedna?

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Families of the Solar System

• Classes of similar objects
• Size
• Composition
• Orbit size
• Orbit shape
• Orbit inclination
• Moons
• Rings

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Families of the Solar System

• Classification
• Structure of the solar system
• Similar objects lie in similar regions
• Clues to solar system formation and evolution

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Sun Rocky Planets Asteroid Belt Gas Giant Plane
ts
Kuiper Belt Oort Cloud
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Sun
Mercury Venus Earth Mars
Asteroid Belt
Jupiter Saturn Uranus Neptune
Kuiper Belt
Oort Cloud
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Some
May View Elaborate Mnemonics
As Boring,
Just Some Useless Nonsensical
Knowledge, But
Others Cheer
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What about Pluto?

• Not a rocky planet
• Not a gas giant planet
• For teachers, it is an opportunity

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Planet Pluto

• 1930 Tombaugh discovers Pluto

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Double Take Charon

• 1978 James Christy (USNO) observations to
  refine Plutos orbit
  
• Notices elongated images, deduces moon
• 1985 Charon occults Pluto, confirms existence
• Refined sizes and masses tiny

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First Pictures of Pluto/Charon

• 1995 Hubble Space Telescope infrared
• 1996 Hubble Space Telescope visible

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First Pictures of Pluto
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Black Sheep of the Planets

• Pluto is the oddball
• Size
• Companion
• Composition
• Orbit
• 32 resonance with Neptune
• Pluto/Charon as double ice planet?

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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

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KBOs

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

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More and more KBOs

• Large searches for KBOs ensued
• Hundreds discovered within a decade
• About 700 so far (Mar 2004)
• Over 70,000 predicted with diameters 100 km,
  orbits 30-50 AU
  
• Plutinos Neptune resonance
• Scattered Neptune affects orbit
• Classsical Separated from Neptune

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Pluto/Charon orbits within Kuiper Belt
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Orbit Comparison Pluto/Charon vs 2004 DW
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Large KBOs

• Pluto still larger, but not by that much
• Note plot below doesnt include Quaoar or Sedna

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Sedna the Inner Oort Cloud?

• Orbit 76 840 AU
• outside Kuiper Belt
• inside Oort Cloud
• Very red color
• Slow rotation

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Binary KBOs

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

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What is Pluto?

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

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Kuiper Belt Experts 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

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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 Jupiters mass
  
• No lower limit specified
• Reasonable lower limit?
• Massive enough for gravity to make it spherical
• At least 14 planets
• No reasonable definition produces 9 planets

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What is a Planet?

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

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Planets around Other Stars

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

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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