Download On the Revolutions of Heavenly Spheres

Not Your Parents’
Solar System!
Dr. Frank Summers
Space Telescope Science Institute
March 28, 2008
Your Ancient Ancestors’ Solar System
Claudius Ptolemy
150 – Almagest
Earth
Moon
Mercury
Venus
Sun
Mars
Jupiter
Saturn
Your Parents’ Solar System
Nicholas Copernicus
1543 – On the Revolutions of Heavenly Spheres
Earth
Moon
Mercury
Venus
Sun
Mars
Jupiter
Saturn
Sun
Mercury
Venus
Earth / Moon
Mars
Jupiter
Saturn
William Herschel
1781 – Discovery of Uranus
Urbain Le Verrier & John Couch Adams
1846 – Prediction and discovery of Neptune
Clyde Tombaugh
1930 – Discovery of Pluto
Your Parents’ Solar System
Your Parents’ Solar System
Mercury
My
Venus
Very
Earth
Energetic
Mars
Mother
Jupiter
Just
Saturn
Served
Uranus
Us
Neptune
Nine
Pluto
Pizzas
Your Parents’ Solar System
Facts Are Not Knowledge
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Memorization, not understanding
Factoids
Highlights differences
Little or no relevance
Little or no “big picture”
The 21st Century Solar System
Sun
Rocky
Planets
Asteroid Belt
Giant
Planets
Kuiper Belt
Oort Cloud
Families of the Solar System
• Classes of similar objects
– Size
– Composition
– Orbit size
– Orbit shape
– Orbit inclination
– Moons
– Rings
Hollywood’s View of the Asteroid Belt
Hundreds of
thousands of
asteroids …
… about a million
miles apart!
960 million miles
Scientific View of the Asteroid Belt
Sizes of the Giant Planets and Earth
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
Figure 1a: Comet Semimajor Axis Distribution
600
Orbital Period:

7 years
200 years
400
Long Period
Short Period
300
200
100
1 / a (1/AU)
0.390
0.185
0.088
0.042
0.020
0.009
0.004
0.002
0.000
-0.002
0
-0.004
Number of Comets
500
Sedna
Sedna
• Orbit 76 – 840 AU
• Very red color
• Outer Kuiper Belt?
• Inner Oort Cloud?
• Planet at 70 AU?
Families of the Solar System
• Classification
• Structure of the solar system
– Similar objects lie in similar regions
• Clues to solar system formation and
evolution
Rocky Planets
Giant Planets
Sun
Rocky
Planets
Asteroid Belt
Giant
Planets
Kuiper Belt
Oort Cloud
Sun
Mercury Venus Earth Mars
Asteroid Belt
Jupiter Saturn Uranus Neptune
Kuiper Belt
Oort Cloud
Science
May View Established Models
As Basic
Justified Standards Until New
Knowledge Bears
Out Changes
Sometimes
My Very Energetic Mother
Also Boils
Jumbo Shrimp Using Nine
Kettles Bubbling
Over Coals
The Inevitable Question …
Why is Pluto No
Longer a Planet?
Planet Pluto
January 23, 1930
January 29, 1930
The Incredible Shrinking Planet
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Lowell’s Planet X – 7 times Earth
1940’s – 1 times Earth
1980 – 0.1 times Earth
1985 – 0.002 times Earth
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
Pluto/Charon
Mimas
Mercury
Iapetus
Miranda
Proteus
Tethys
Dione
Umbriel
Europa
Moon
Pallas
Ariel
Io
Hygeia
Triton
Titan
Ganymede
Vesta
Oberon
Callisto
Ceres
Rhea
Titania
Enceladus
Pluto
Charon
Kuiper Belt
• 1930 – Leonard mentions possibility of transPlutonian 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 ‘comet belt’ that
resembles what was eventually found
Kuiper Belt Objects
• 1992 – Jewitt & Luu
find QB1
• Distance of 42 AU
• First (third?) object
discovered in the
Kuiper Belt
Kuiper Belt
More and more KBOs
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Large searches for KBOs ensued
Hundreds discovered within a decade
Over 1200 discovered so far
Over 70,000 predicted
– diameters > 100 km
– orbits 30-50 AU
Pluto Defenders
• Pluto is different from the KBOs
• Pluto is bigger than the KBOs
• Pluto has a moon, Charon
Pluto/Charon orbits within Kuiper Belt
KBO Size Comparison
Binary KBOs
• About 10% of KBOs are binaries
Eris & Dysnomia (2003 UB313)
Easterbunny
Santa & Rudolph
Eris & Dysnomia
Pluto vs the Kuiper Belt
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Orbit similar to KBOs
Size similar to KBOs
KBO companions common
Composition similar to KBOs
Pluto vs the Kuiper Belt
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Orbit similar to KBOs
Size similar to KBOs
KBO companions common
Composition similar to KBOs
Pluto has found its family!!
IAU Definition – August 2006
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IAU defines “planet”
1. Orbits the Sun
2. Upper mass limit
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not massive enough to produce fusion
Deuterium fusion occurs at about 15x Jupiter’s mass
3. Lower mass limit
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Massive enough for gravity to make it spherical
About 500 miles in diameter
4. Dominates its orbit
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Dwarf planets meet 1, 2, 3, but not 4
Other Planetary Systems?
• Solar system alone is category of one
Beta Pictoris
We Are Not Alone
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Lots of dust disks found
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)
– Giant planets detectable
Planets around Other Stars
• Current count (May 2006)
– 162 planetary systems
– 188 planets
– 19 multiple planet systems
• At least 15% of sun-like stars have
planets
Planets around Other Stars
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Jupiter mass planets in Mercury orbits
Elliptical orbits
Multiple Jupiter sized planets
Planets around pulsars
Smallest (so far) is about 5 Earth
masses
Planetary System Formation
• Planetary systems form in a predictable
fashion from a spinning circular disk
Sun
Rocky
Planets
Asteroid Belt
Giant
Planets
Kuiper Belt
Oort Cloud
So Much 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