2nd Midterm: Mean: 85 St.Dev: 11 For help: For help: See GSI or Prof. Manga or Prof. Marcy

2nd Midterm: Common Mistakes 1. Greenhouse Effect: CO2 absorbs IR light (not UV). 2. Geological activity on Jupiter’s moons is due to their composition of ice: Allows melting at low temperatures in the outer solar system. Volcanism and tectonics possible.

Announcements Homework due a week from Friday: Chapter 13 on Planets Around Other Stars Homework counts 50% of grade; Drop lowest score. Final Exam - comprehensive: May 8am: 237 Hearst Gym Telescope Observations: Saturn, Mars, Orion Nebula. Observing Starts: 8pm ! Star Chart with 3 obs of Mars: Due May 1.

Wednesday, April 23, 5:30pm Chevron Auditorium - International House "The Dawn of Creation: The First Two Billion Years" A Special Lecture by Steven Beckwith Extra Credit: 3 points for half-page summary of talk

Are there Other Planetary Systems ? Are any of them like our Solar System ? like our Solar System ?

February 5, 1996

Now Exiting our Solar System to … The Milky Way Galaxy Now Leaving our Solar System...

Democritus: Greek philosopher ( BC). Greekphilosopher BC “ There are innumerable worlds of different sizes. These worlds are at irregular distances, more in one direction and less in another, and some are flourishing, others declining. Here they come into being, there they die, and they are destroyed by collision with one another. Some of the worlds have no animal or vegetable life nor any water. “

Epicurus ( B.C.) “There are infinite worlds both like and unlike this world of ours... we must believe that in all worlds there are living creatures and plants and other things we see in this world…” Greek philosopher in Athens where he opened a school of philosophy

Bruno was enthusiastic about the Copernican theory that the planets circle the sun and he believed there are many other planets around other stars, some of them with life. Giordano Bruno 1584 Giordano Bruno lost the thread of truth and the Roman Church burned him for it. Wrote; ‘ De l'infinito, universo e mondi (The Infinity, the Universe and Its Worlds) Burned at the Stake February 17, 1600 By Catholic Church

Stars are a billion times brighter…

…than the planet hidden in the glare. Detecting Earths: Like detecting a firefly next to a nuclear explosion

Planet Detection The Wobble of a Star: Gravitational pull by the planet Star moves slower, due to conservation of momentum: mass x velocity M STAR V STAR = M planet V planet

1/2 m PL V PL 2 = G m PL M Star / r V PL ~ 10 km/s V Star = V PL V STAR ~ 10 m/s V Star = V PL V STAR ~ 10 m/s x (M PL /M JUP ) x (M PL /M JUP ) Momentum: Wobble Velocity Wobble Velocity M PL M PL M STAR M STAR ( )

Detecting a Star’s Wobble: Doppler Effect Detecting the wobble of a Star, pulled around by its planet. Spectrumstarlight

12 years... Jupiter (Meters/sec) Need Telescope...

Echelle Spectrometer CCD Echelle Grating Collimator Starlight From Telescope High Resolution ``Echelle” Spectrometer

Spectrum of Star: Doppler Effect Doppler Shift:  = v / c 4096 Pixels

Michel Mayor & Didier Queloz 51 Peg Claim of First Detected Extrasolar Planet: 51Pegasi Orbital Period = 4.2 days ! Absurd

One week Later... 4 Nights at Lick Observatory October 11, 1995

Period = 4.2 days Kepler’s 3rd Law: P 2 = a 3 Units: P in years, a in AU Solve for a: a = 0.05 AU Proximity: Temp = 1500 C Determination of Orbital Distance from Star to Planet

Determination of Planet’s Mass Conservation of Momentum: momentum of star = momentum of planet M STAR V STAR = M planet V planet Solve for Mass of planet: M planet = M STAR V STAR / V planet M STAR : Star Masses are known (most are Sun-like) V STAR from Doppler shift: 55 m/s What is V planet ? V planet = 2  a / P You know “a” from Kepler’s 3rd Law: P 2 = a 3 Can Determine M planet

Summary of Doppler Wobble Method : Orbital Physics Kepler’s 3rd Law and Conservation of Momentum P 2 = 4  2 /[G(M star + M planet )] a 3 P = orbital period a = orbital distance of planet from star Simple Version of Kepler’s 3rd Law: P 2 = 4  2 /GM star a 3 ( planet’s mass is negligible compared to star.) Measure P from Doppler periodicity: Can solve for a. Circular Orbit: V planet = 2  a / P (Circumference/Time) Momentum Conservation: M star V star = M Planet V planet M planet = M star V star / V Planet

Doppler Wobble Method : Unknown Orbital Inclination Tilt of Planet’s Orbital Plane: Unknown Edge-on Orbit: Full Doppler EffectEdge-on Orbit: Full Doppler Effect Face-on Orbit: No Doppler EffectFace-on Orbit: No Doppler Effect General Tilt Angle: True Wobble speed isGeneral Tilt Angle: True Wobble speed is greater than Doppler indicates greater than Doppler indicates True planet mass is GREATER than the mass found by the Doppler method. (25% greater on Avg.) We measure M sin i

Period = 4.2 days Kepler’s 3rd Law: P 2 = a 3 Units: P in years, a in AU Solve for a: a = 0.05 AU Proximity: Temp = 1500 C 51 Pegasi First Extrasolar Planet

16 Cygni B Mass = 1.7 M JUP (Min) Orbit Period 2.2 yr Not Sinusoidal VelocityWobble

Velocity

Orbit of Planet around 16 Cygni

16 Cygni: Planet & Moon

Life on Gas Giant Planets ? Floaters Earth-Like Moon

Eccentric Orbit ! of Planet around 16 Cygni

Orbital Eccentricities = 0.25 Tidal Circ. Origin of Eccent. Unknown

Origin of Eccentricities Ford & Rasio 2006 Planet - Planet Gravitational Interactions

Mass = 0.62 M JUP 70 Days

Upsilon Andromedae : Velocity Residuals

0.6 M JUP 2 M JUP 4 M Jup Upsilon Andromedae: Triple Planet System Planets have No Names

Upsilon Andromedae