Are There Other Worlds?Modern Answers to a

2500-year-old Question

Charles Beichman, Michelson Science Center

JPL/California Inst. of Technology

From Greek Philosophers ...

“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.”--- Epicurus (c. 300 B.C)

“I [regard]… as false and damnable the view of those who would put inhabitants on Jupiter, Venus, and Saturn, and the moon, meaning by ‘inhabitants’ animals like ours and men in particular.”

…to Renaissance Scholars...

…and Martyrs..."There are countless suns and countless earths all rotating around their suns in exactly the same way as the seven planets of our system. We see only the suns because they are the largest bodies and are luminous, but their planets remain invisible to us because they are smaller and non-luminous. The countless worlds in the universe are no worse and no less inhabited than our Earth”Giordano Bruno (1584) in De L'infinito Universo E Mondi

…To Hollywood Producers…Is There Intelligent Life on Earth?“Klaatu Borada Nikto”

“Your choice is simple. Join us and live in peace or pursue your present course and face obliteration. We shall be waiting for your answer. The decision rests with you.”

203 RV Planets 14 Transit Planets

Heat from Transiting Jupiters Comet & Asteroid Belts

Transit Spectra

… We are Using 21st Century Tools to Address 2,500 Year Old Questions

Hot Young Jupiters

Radial Velocity (Doppler) Technique --- Most Productive to Date

• 203 planets, incl 20 multiple systems, and counting with Keck/HIRES ---the premier planet finding telescope in the world

• Finding “Hot Earths”possible with RV, but not “Habitable Earths”

What is a Potentially Habitable Planet? The Goldilocks Zone

Kasting et al 1993

• Surface temperature suitable for liquid water:– Habitable Zone (HZ)

ranges from orbit of Venus (too hot) to orbit of Mars (too cold)

• Mass/radius large enough to hold an atmosphere, but not so large for runaway growth (0.5-10 Mearth)

• Small orbit eccentricity for stable temperature • No giant planets swinging through

So Where is the Habitable Zone?

This is it!800 Astronomers Gathered in The Most Habitable Zone

in the Solar System to Discuss The Habitable Zone

K. Teramura and W. Wang

How Do We Find Habitable Earths?

SIMRV 1m/s

Kepler@1Kpc0.5%

NASA’s SIM-PlanetQuest

• SIM will extend Keck’s RV program to identify earth-like planets in Habitable Zones of 120 stars within 100 light years

Transit Method:1 Planet Hides Star

• Transit depth: 1% (Jupiter) to 0.01% (Earth)• Alignment probability: 1% ~ 10% • Look for transit in RV systems• Find new transits and confirm with RV (Keck)

Transit Method-2: Star Hides Planet

What Do We Learn from Transits?• Visible Transits

– Radius– Density– Composition– Moons or other planets

• Infrared Transits– Temperature, reflectivity

and composition– Rotation, winds

• Much more to come– Ground-based surveys for

giant planets (Pan STARRS)

– COROT and Kepler for super-Earths and Earths

– JWST follow-up

Swain et al 2007; Richardson et al 2007; Grillmair et al 2007

Direct Measurement of Light From Another Planet

Planetary Systems Should Be Common ---But Many Details Uncertain

Birth of Planets, Asteroids and Comets• Disks of gas and dust surround most young stars• Gas disks dissipate after 10 Myr --- gas giants must have

formed and migrated into final orbits• Most solid material dissipates by few 100 Myr --- terrestrial

planets must have formed by then• Over ~100 Myr volatile organic molecules, ices, and water are

brought in from outer reaches to make habitable environments

Werner et al 2003

HR 4796

GG Tau

Keck astronomers are in forefront of major theoretical and observational effort to understand how, where, and when stars and planets form

Probing The Birthplace of Stars and Planets: The Keck Interferometer

• KI combines two 10-m telescopes to make a single “super-telescope” with an 85-m equivalent aperture– Protostellar and protoplanetary disks around young stars– Debris Disks around mature stars– Masses of young stars in binary systems

How Does The Interferometer Work?

Keeping Keck At The Forefront• Combine KI with Adaptive Optics using NSF grant (Peter

Wizinowich, WMKO, and James Graham, UCB)– Search for Jupiters around nearby & young stars– Probe inner disks where planets must be forming

• Combine the 7 large telescopes on Mauna Kea to make 800 m (!) telescope called OHANA to make images of stars and disks

Debris Disks Are Remnants of Planetary System Formation• Asteroid belts and comet

(Kuiper) belts found around 15% of nearby stars

• Structures in disks reveal presence of planets

• Cold debris disks sources of volatiles needed for life

AU Mic (Keck II AO) --- Liu et al 2004

Fomalhaut (HST) ---Kalas et al 2006

We Live Inside A Debris Disk

• Interplanetary dust particles are released by asteroid collisions & cometary passages

• Within a few AU, dust arising from collisions in the asteroid belt is heated to ~250K

• Beyond the asteroid belt, dust arises from cometary debris originating in the Kuiper Belt

COBE 3 μm COBE 25 μm

Spitzer Finds A “Green Sand”Asteroid Belt

Beichman et al 2006Lovis et al 2006; Lisse et al 2007

3 Uranus Mass Planets!

Ultimate Goal to Search for Life On Distant Earths

• Collecting area of 6 m telescope in space• Angular resolution for habitable zone at 30 ly:

~8 m telescope in visible or ~80 m IR interferometer• Extreme contrast ratio

≈1010

TPF-CTPF-I

≈107

Stars are a billion times brighter…

…than the planet

…hidden in the glare.

Like this firefly.

Intermediate Steps: Imaging Jupiters From

the GroundUse advanced Adaptive Optics (including Laser AO) to search for Brown Dwarfs and (young) Jupiter mass planets using Keck and other telescopes

Metchev and Hillenbrand 2006 VLT Hot Jupiter

TWA-5--- Quinn Konopacky and Andrea Ghez, UCLA

Following The Orbits of Young Binary Stars From Keck

Better Orbital Measurements for Lower Mass Objects (Planets) with TMT

TWA-5--- Quinn Konopacky and Andrea Ghez, UCLA

Finding Jupiters from the Ground--- The Next Generation

Advanced Coronagraph on Thirty Meter Telescope (TMT) could find nearest Jupiters in reflected light

Gemini Planet ImagerTMT Planet ImagerTPF

Telescopes To Find Earths and LifeWill (Eventually) Be in Space

TPF-Coronagraph (TPF-C) TPF-Interferometer(TPF-I)/ESA Darwin

External Occulter (TPF-O)

Many Different Measurements Required for Planet Characterization• Stable orbits in HZ

–Temperature Variability• Habitability

–Mass–Radius–Albedo–Surface gravity–Temperature–Composition

• Solar System–Influence of other planets–Comets or asteroid belts

• Indicators of Life–Atmospheric signatures (O2, O3, CH4)–Surface signatures (chlorophyll)

And How Will We Know A Planet Supports Life?

Look for evidence of oxygen

Look for liquid water

Analyze the reflected light from the planet to see if the planet has an atmosphere

Look for signs of biological activity (methane)

And Rule Out Other Explanations?17

Signs of Life on Earth: NIMS Data (from Galileo)

Sagan et al. (1993), Toby Owen (1980)

Thermal IR spectra

Ref: R. Hanel, GSFC

Strong Scientific and Public Support For Nation’s Planet Finding Program

The 2000 National Academy Review

NASA’s Vision for Space Exploration

“Conduct advanced telescope searches for Earth-like planets and habitable environments around other stars”

“Search for life beyond Earth, and if it is found, determine its nature and its distribution [in the Galaxy]”

From Jupiters to Earths:From Ground And Space

Mauna Kea

TMT

SIM PlanetQuest

Terrestrial Planet Finder/Darwin

We shall not cease from explorationAnd the end of all our exploringWill be to arrive where we startedAnd know the place for the first time.Through the unknown, unremembered gateWhen the last of earth left to discoverIs that which was the beginning; ----T.S. Eliot, Four Quartets

A Pale Blue Dot