John Bally 1 1 Center for Astrophysics and Space Astronomy Department of Astrophysical and Planetary Sciences University of Colorado, Boulder Searching for Other Worlds: Searching for Other Worlds:

The Search for Exo-planets: The Search for Exo-planets: The Context: The Age of Discovery - Our generation is charting the Universe! - Origns of the cosmos, stars, planets, and life How common are terrestrial (habitable) planets? - Star and Planet Formation - Astrobiology: The origins of life on Earth In-situ searches in the Solar System Remote-sensing biosignatures Methods of Discovery: Past, present, future (Saturday talk). - Astrometry - Radial velocity - Transits - gravitational lensing - Direct detection, imaging, characterization Mission Development: From Concept to Flight to Science - COROT, Kepler, SIM, TPF, Darwin, Starshade, Planet Imager, ….

The Age of Astronomical Discovery The Age of Astronomical Discovery Access to all wavelengths of the spectrum - Silicon technology => sensors at most wavelengths - Large telescopes Powerful computers Access to space - No atmosphere => Sharp images (Hubble Space Telescope) => Access to all wavelengths (Spitzer) Connections to Physics - Scales: to cm, to sec - 4 forces: gravity, electro-magnetism, weak, strong - Matter (4%), Dark matter (24%), Dark energy (72%)

The Evolution of the Universe: The Evolution of the Universe: Cosmology: Baryons = 4% 13.7 Gyr Dark Matter = 26% (1 Gyr = 10 9 years) Dark Energy = 70% Cosmic Microwave Background: The young Universe 400,000 years Hot, ionized plasma 3,000 Kelvin (1/2 temperature of Sun) Smooth to 1:10 5 The Cosmic Dark Ages: – 0.6 Gyr The First Stars: Massive 0.6 – 1 Gyr Formation of Galaxies > 1 Gyr Solar System Formation: 9.1 Gyr Star & Planet Formation today

Dark Energy: Expansion is accelerating!

Stars Stars Stars: The fundamental building blocks of the Universe High mass: ( times Mass of Sun) Short lived: < 30 million years Source of energy in interstellar medium Explode as supernovae Long Lived: > Billion years (Lock up mass for long time) Luminous: Thousand => million times Sun Faint: Planets: Abodes of life Sources of light, chemical elements Low Mass: (< 2 times Mass of Sun)

Introduction Introduction Star Formation: The fundamental cosmic (baryonic) process Determines cosmic fate of normal matter Star Formation Galaxy formation, evolution, IMF Elements (He => U) Clusters black holes (AGN, stellar) Light, K.E. of ISM Planet formation Conditions for life

M16 4 million Year-old Cluster + Ionized Nebula + Surviving cloud

M16 (HST) Surviving cloud

Where planets also form Giant Molecular Cloud Core Gravitational Collapse & Fragmentation Rotation & Magnetic Fields Raw material for star birth Proto-stars, proto-binaries, proto-clusters Accretion disks, jets, & outflows Shrink size by 10 7 ; increase density by x ! Star Formation Star Formation Planets C. Lada Most may form in clusters!

Orion Nebula

Orion near-IR (Feigelson et al. 2005)

COUP X-rays (Feigelson et al. 2005)

Flux History, Typical 1 M o Star Punctuated equilibrium at its finest! Flux varies by 1000x Peak flux approaches 10 7 G 0. Intense close encounters with core. There is no `typical UV flux.’ Impulsive processing.

d in M43 Smith et al. 05 Planets in Formation?

Young Proto-planetary Disk

HST 10 HST 17 How common are close approaches? 1” = 500 AU Bally et al. 98 HST AU diameter HST AU diameter 0.3 ly to O star

Anatomy of a planetary system forming in an OB association

Sedimentation + Photo-Evaporation Self-irradiation Gap opened at r = GM/c 2 Viscous evolution + Radial migration moves dust into gap Large dust:gas => planetesimals

Stellar Reflex Motion: - Periodic Doppler variation ground-based spectroscopy - Periodic Position change astrometry => space interferometry Transits (planet blocks light) Kepler, TESS Gravitational Lensin precission photometry Direct detection in images coronagraphs, starshades The Search Extra-Solar Planets Hard: Earth (10 billion) x fainter than Sun!

Direct imaging of exo-planets is Hard: 10 Sun Earth

> 200 planets: Most located inside Earth’s orbit Goeff Marcy Paul Butler Earth radial velocity method

200 planets: Gas Giants like Jupiter > 200 planets: Gas Giants like Jupiter

Orbit eccentricity

The Metallicity Effect:

Stellar Reflex Motion: - Periodic Doppler variation - Periodic Position change Transits (planet blocks light) Gravitational Lensing Direct detection in images The Search Extra-Solar Planets Hard: Earth (10 billion) x fainter than Sun!

Quantitative estimate of reflex motion: D*D* DpDp CM M*M* mpmp mpmp = D p M*M* D p ~ r orbit D*D* D * = (m p /M * ) r orbit V * = (m p /M * ) V orbit

Reflex Motion: To Earth Planet Parent Star Center of Mass

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

Reflex Motion: To Earth

D * = (m p /M * ) r orbit M Earth = 6 x g M Jupiter = 1.7 x g M Sun = 2 x g D Earth = 1.5 x cm (1AU) D Jupiter = 7.8 x cm Quantitative estimate of reflex motion: 1AU 4.5 x 10 7 cm 1AU 1.3 x cm 5.2 AU 6.6 x cm

- Midterm #2 Next Friday - Return mid-term / solutions posted - HW#5 posted: Due Monday searching for and characterizing exo-planets Searching for Other Worlds: Searching for Other Worlds:

Midterm #1 scores

Stellar Reflex Motion: - Periodic Doppler variation - Periodic Position change Transits (planet blocks light) Gravitational Lensing Direct detection in images The Search Extra-Solar Planets Hard: Earth (10 billion) x fainter than Sun!

Quantitative estimate of reflex motion: Orbital speed of planet: V p = (GM * / D p ) 1/2 Orbital speed of star: V * = V p (D * / D p ) VpVp V*V* D*D* DpDp 1AU 8.9 cm/s 1AU 25.4 m/s 5.2 AU 11.1 m/s V*V*

The Doppler Effect:   =  = V * / c (v << c) 1AU 8.9 cm/s 3 x AU 25.4 m/s 8 x AU 11.1 m/s 4 x V*V*  Frequency  Wavelength  c  speed of light  

The Sun’s Wobble

The first exo-planets: Use radio timing of Pulse-arival - Doppler Time (days) Brightness

Time (days) 124 Radial velocity (m/s) Velocity variation of 51 Peg (Doppler shift) Goeff Marcy, Paul Butler

Gas-Giants Close-In: “Hot Jupiters” Oribital Periods: 1 day => 1 year D ~ 0.05 AU to > 1 AU T ~ 1400 K to < 300 K Giants => Composed of H, He (like Jupiter) Evaporation of outer H in atmosphere Earth-like planets, moons ?

Transits:

Transit decreases light of star Time (days) Transits:

Kepler: Kepler: Transits

First planet Discovered Using the Transit method

Transit of HD209458b (HST)

UV absorption: Escaping H and Na Detected towards HD Recently, C and O Have been detected - escaping atmosphere!

A cluster of galaxies `lensing’ more distant objects … Gravitational Lensing: A star & its planets magnifying a more distant star

Gravitational Lensing: Star and planet magnifies background starlight Gravitational Lensing: Magnification by star Magnification by planet Time (days) Brightness

Gravitational Lensing : OGLE 2003-BLG0253 Brightness

Gravitational Lensing: Brightness

-20 Radio emission: Jupiters +200 Time (days) Brightness

Exo-planet detection methods

- Midterm #2 Next Friday - Return mid-term / solutions posted - HW#5 posted: Due Monday searching for and characterizing exo-planets Searching for Other Worlds: Searching for Other Worlds:

Methods for direct detection and characterization of exo-planets : Direct imaging with a coronagraph: UV, visual, near IR Mask light of star control scattered light, diffraction Large filled-aperture telescope Interferometry IR, radio Link several telescope pre-detection/post-detection

Ground vs. Space: Ground: - 10 – 100 meter vis/NIR - Extreme adaptive optics to correct turbulent images - radio interferometry (VLA, eVLA, SKA) Space: - 10 m + UV,VIS, NIR - Interferometers

Future Projects for finding Planets: Kepler: transits (2008+) Atacama Large Millimeter Array (ALMA): mm interferometer: direct detection of young gas giants Next Generation Space Telescope James Webb Space Telescope (JWST): - direct imaging of forming gas giants? Space Interferometry Mission (SIM): - Astrometry (“defered”) Terrestrial Planet Finder (TPF): (“defered”) - Coronagraph - IR interferometer - Star Shade (Web Cash et al.) Terrestrial Planet Imager (TPI): (?)

ALMA (Atacama Large Millimeter Array)

Next Generation Space Telescope & test - Large next-generation space telescopes (near-infrared & visual wavelength) block parent star's light

Finding planets around other stars: (2010+) -Space Interferometry Mission (SIM) measure stellar `wobble’ - Terrestrial Planet Finder (TPF) Direct detection of Earth-sized planets - Infrared `interferometer’ or - visual `coronagraph’ Darwin interferometer

Diffraction pattern of a circular aperture

Shaped telescopes: 0.3 < l < 3 mm Shaped telescopes: 0.3 < l < 3 mm Circular aperture diffracts light in all directions. - Light is scattered perpendicular to edges. Shaped aperture: Edges have limited orientations - Scatter light only into selected (unwanted) directions

Diffraction patterns of shaped apertures

Earth as seen from 10 pc with various interferometers

Biosignatures: Spectra of various planets IR (Stratosphere) vs. visible (Ground)