Not Your Parents’ Solar System!
Dr. Frank Summers Space Telescope Science Institute
July 11, 2013
Your Ancient Ancestors’ Solar System
Earth
Moon
Mercury
Venus
Sun
Mars
Jupiter
Saturn
Claudius Ptolemy 150 – Almagest
Misconception
• Ptolemy invented the Earth-centered solar system.
Misconception
• Ptolemy invented the Earth-centered solar system.
• Ptolemy organized and systematized the Earth-centered solar system based on ideas that had been developed over about 600 years.
Your Parents’ Solar System
Nicholas Copernicus 1543 – On the Revolutions of Heavenly Spheres
Misconception
• Copernicus delayed publishing because he feared criticism from religious leaders.
Misconception
• Copernicus delayed publishing because he feared criticism from religious leaders.
• Copernicus delayed publishing (in part) because he feared criticism from scientists.
Earth
Moon
Mercury
Venus
Sun
Mars
Jupiter
Saturn
Sun
Mercury
Venus
Earth / Moon
Mars
Jupiter
Saturn
Misconception
• Copernicus’ Sun-centered solar system was quickly accepted because it was much simpler and more accurate.
Misconception
• Copernicus’ Sun-centered solar system was quickly accepted because it was much simpler and more accurate.
• Copernicus’ Sun-centered solar system was just as complex as Ptolemy’s Earth-centered solar system, and provided no more accuracy in its predictions.
Galileo 1609 – Use of telescope for astronomy
1632 – Trial by the Inquisiton
Misconception
• Galileo invented the telescope and was the first to use it for astronomy.
Misconception
• Galileo invented the telescope and was the first to use it for astronomy.
• Galileo was one of several folks who improved the spyglass so that it could be used for astronomy.
Misconception
• Galileo proved that Copernicus’ Sun-centered solar system was correct.
Misconception
• Galileo proved that Copernicus’ Sun-centered solar system was correct.
• Galileo tried to prove Copernicus’ Sun-centered solar system, but his arguments were wrong.
Tycho Brahe 1546-1601
Johannes Kepler 1571-1630
Misconception
• Astronomers embraced the Sun-centered solar system because it is philosophically simpler.
Misconception
• Astronomers embraced the Sun-centered solar system because it is philosophically simpler.
• Astronomers embraced the Sun-centered solar system only when it could provide better predictions.
Isaac Newton 1687 – Principia
William Herschel 1781 – Discovery of Uranus
1801 – Planet Ceres (Piazzi)
1801 – Planet Ceres (Piazzi)
1802 – Planet Pallas (Olbers)
1804 – Planet Juno (Harding)
1807 – Planet Vesta (Olbers)
1845 – Planet Astraea (Hencke)
Urbain Le Verrier & John Couch Adams 1846 – Prediction and discovery of Neptune
Rocky Planets Giant Planets
Misconception
• You can’t just demote a planet!
Misconception
• You can’t just demote a planet!
• In the mid-1800’s, astronomers demoted the many planets between Mars and Jupiter to be asteroids.
Clyde Tombaugh 1930 – Discovery of Pluto
Misconception
• Pluto’s discovery relied on mathematical predictions based on perturbations in Neptune’s orbit.
Misconception
• Pluto’s discovery relied on mathematical predictions based on perturbations in Neptune’s orbit.
• Pluto’s discovery relied solely on the incredible observing skill and dedication of Clyde Tombaugh. – Neptune’s orbit shows none of the claimed
perturbations.
Your Parents’ Solar System
Your Parents’ Solar System
Your Parents’ Solar System
Mercury Venus
Earth Mars
Jupiter Saturn
Uranus Neptune
Pluto
My Very
Energetic Mother
Just Served
Us Nine
Pizzas
Facts Are Not Knowledge
• Memorization, not understanding • Factoids • Highlights differences • Little or no relevance • Little or no “big picture”
Comparative Planetology
An Improvement
• Compare and contrast – Discuss broad ideas – Apply to planets, moons, etc., as a group
• Highlight similarities – Appearance – Characteristics – Events
April 1997 September 1997
Planetary Comparisons • Canyons – Grand Canyon, Mariner Valley • Volcanoes – Mount St. Helens, Olympus
Mons, Io • Craters – Earth, Moon, Mercury, …
• Storms, Winds, Seasons, Weather, Ice Floes, Magnetic Fields, Moons, Rings, etc
Comparative Planetology
• Messages – What happens on Earth happens
elsewhere – Solar system is understandable
• Pieces to assemble the big picture
Sun
Rocky Planets
Asteroid Belt
Giant Planets
Kuiper Belt
Oort Cloud
The 21st Century Solar System
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
Scientific View of the Asteroid Belt
960 million miles
Hundreds of thousands of asteroids …
… about a million miles apart!
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
0
100
200
300
400
500
600-0
.004
-0.0
02
0.00
0
0.00
2
0.00
4
0.00
9
0.02
0
0.04
2
0.08
8
0.18
5
0.39
0
1 / a (1/AU)
Num
ber
of C
omet
s
Short PeriodLong Period
Orbital Period: 200 years∞ 7 years
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
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
Science
Out Changes
May View Established Models
As Basic
Justified Standards Until New
Knowledge Bears
Sometimes
Over Coals
My Very Energetic Mother
Also Boils
Jumbo Shrimp Using Nine
Kettles Bubbling
The Inevitable Question …
Why is Pluto No Longer a Planet?
Planet Pluto
January 23, 1930 January 29, 1930
Pluto/Charon
1978 – James Christy (USNO)
The Incredible Shrinking Planet
• Lowell’s Planet X – 7 times Earth • 1940’s – 1 times Earth • 1980 – 0.1 times Earth • 1985 – 0.002 times Earth
Kuiper Belt Objects
• 1992 – Jewitt & Luu find QB1
• Distance of 42 AU • First (third?) object
discovered in the Kuiper Belt
Kuiper Belt
But Isn’t Pluto Special in Some Way?
Orbit Comparison: Pluto/Charon vs 2004 DW
Kuiper Belt
Moon
Eris & Dysnomia Haumea, Hi’iaka & Namaka
Makemake
KBO Size Comparison
Pluto vs the Kuiper Belt
• Orbit similar to KBOs • Size similar to KBOs • KBO companions common • Composition similar to KBOs
Pluto vs the Kuiper Belt
• Orbit similar to KBOs • Size similar to KBOs • KBO companions common • Composition similar to KBOs
Pluto has found its family!!
IAU Definition – August 2006 • IAU defines “planet”
1. Orbits the Sun 2. Upper mass limit
• not massive enough to produce fusion • Deuterium fusion occurs at about 15x Jupiter’s mass
3. Lower mass limit • Massive enough for gravity to make it spherical • About 500 miles in diameter
4. Dominates its orbit • Dwarf planets meet 1, 2, 3, but not 4
Other Planetary Systems?
• Solar system alone is category of one
HR 8799
Planets around Other Stars
• Jupiter mass planets in Mercury orbits • Elliptical orbits • Multiple Jupiter sized planets • Planets around pulsars
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
Presentation Materials
• Online Sessions – Google Hangout September – Info to come
• Social media – Facebook.com/DrFrankSummers – Twitter @drfranksummers
http://tinyurl.com/PA-GSFC-2013