Not Your Parents’ Solar System! Dr. Frank Summers Space Telescope Science Institute March 28, 2008 It’s

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

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto My Very Energetic Mother Just Served Us Nine Pizzas

Your Parents’ Solar System

Facts Are Not Knowledge Memorization, not understanding Factoids Highlights differences Little or no relevance Little or no “big picture”

Sun Rocky Planets Asteroid Belt Giant Planets Kuiper Belt Oort Cloud The 21 st 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

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 PlanetsGiant Planets

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

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, 1930January 29, 1930

The Incredible Shrinking Planet Lowell’s Planet X – 7 times Earth 1940’s – 1 times Earth 1980 – 0.1 times Earth 1985 – 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

Pluto Triton Titan Callisto Ganymede Moon Io Europa Mercury Rhea Iapetus Titania Oberon Pallas Vesta Hygeia Mimas Enceladus Miranda Proteus Ceres TethysDione Ariel Umbriel Charon

Kuiper Belt 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 ‘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 Large searches for KBOs ensued Hundreds discovered within a decade Over 1200 discovered so far Over 70,000 predicted –diameters > 100 km –orbits 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

Sidebar: Is the Moon a Moon? Earth Moon

Binary KBOs About 10% of KBOs are binaries

Eris & Dysnomia (2003 UB313)

Eris & DysnomiaSanta & Rudolph Easterbunny

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

Beta Pictoris

We Are Not Alone 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 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