Not Your Parents Solar System

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Not Your Parents Solar System!

• Frank Summers
• Space Telescope Science Institute
• March 1, 2005

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First Pictures of Pluto
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Your Parents Learned

• The solar system consists of the Sun and nine
  planets

Wrong!
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Wrong and Bad

• Memorization, not understanding
• 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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Still Not Good Enough

• 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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The 21st Century Solar System

• Six families in the solar system

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

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Sedna

• Orbit 76 840 AU
• Very red color
• Slow rotation
• Outer Kuiper Belt?
• Inner Oort Cloud?
• Planet at 70 AU?

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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
Planets 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?

• Pluto is the ninth planet

Wrong!
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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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Io
Mercury
Europa
Moon
Triton
Titan
Ganymede
Callisto
Pluto
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Plutos Family?

• Pluto is not a Rocky Planet
• Pluto is not a Gas Giant Plant
• Pluto is an oddball
• Size
• Companion
• Composition
• Orbit
• 32 resonance with Neptune

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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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Kuiper Belt Objects

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

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Kuiper Belt
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More and more KBOs

• Large searches for KBOs ensued
• Hundreds discovered within a decade
• About 800 so far (March 2005)
• Over 70,000 predicted with diameters 100 km,
  orbits 30-50 AU

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Pluto Defenders

• Pluto is different from the KBOs

Wrong!
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Orbit Comparison Pluto/Charon vs 2004 DW
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Pluto/Charon orbits within Kuiper Belt
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Size Comparison

• Pluto currently largest, but not by much
• Note plot below doesnt include Quaoar or Sedna

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But Pluto is Still Special

• Pluto has a moon, Charon

Wrong!
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Sidebar Is our Moon a moon?
Earth
Moon
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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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Pluto vs the Kuiper Belt

• Orbit similar to KBOs
• Size similar to KBOs
• KBO companions common
• Composition similar to KBOs

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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 Pluto 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 13 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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Beta Pictoris
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We Are Not Alone

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

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Planetary System Formation

• Planetary systems form in a predictable fashion
  from a spinning circular disk

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

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Planets around Other Stars

• Current count (Apr 2004)
• 105 planetary systems
• 120 planets
• 13 multiple planet systems
• At least 15 of sun-like stars have planets

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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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So Much for You to Discover

• 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

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Let the Quest Begin!
http//terpsichore.stsci.edu/summers/ - or
- Google Frank Summers

• Writings
• Not Your Parents Solar System