NASA: How to Become a Planet Hunter: Careers in Space Science€¦ · Knowledge and Ignorance of Extrasolar Planets What we do know – Giant planet occurrence is high: ~7% – Mass

LIVE INTERACTIVE LEARNING @ YOUR DESKTOP

May 24, 2012

NASA: How to Become a Planet Hunter: Careers in Space Science

Presented by: Dr. Stephen Edberg

Exoplanet Discovery and Exploration: Expanding Geography Outside Our Solar System

Stephen J. Edberg

Exoplanet Exploration DirectorateNASA Jet Propulsion LaboratoryCalifornia Institute of Technology

There are 200 billion stars in our galaxy…

…one of them is our Sun.

The Sun has eight (or nine) planets…

…we know of one that has life.

What about elsewhere?

There is a role for everyone who wants to be a part of this great exploration.

Contributors include:

astronomers planetary scientists physicistsmathematicianscomputer scientistsengineers

artistseducatorspublic affairs officersbusiness managersand others

Stars are a billion times brighter…

…than the planet

…hidden in the glare.

Like this firefly.

Planet Discovery Methods

• Direct Imaging (Vis & IR)

• Radial Velocity

• Transits

• Gravitational Microlensing

• Astrometry

• Pulsar Timing

Planets by Direct Imaging

NO

Radial Velocity - 1

BLUE

Radial Velocity - 2

Radial Velocity - 3

RED

Radial Velocity - 4

Single Line “Binary” - Planet

540-775 nm

Star Spectrum

Iodine Spectrum

Planets by Radial Velocity:Actual Observation Method

Planets by Radial Velocity

Single Line “Binary” - Planet

Without Iodine Cell

Planets by Transit - 1

Planets by Transit - 2

Kepler Spacecraft

Transit Geometry

z

T( z, λ)

By observing the spectrum of the star + planet as the planet transits, we can determine the height of the atmosphere where it becomes opaque and determine its chemical composition.

19Traub

Starlight passing through the planet’s atmosphere.

Transit/Occultation Weather Map

astronomersplanetary scientists physicistsmathematicianscomputer scientistsengineersartistseducatorspublic affairs officersbusiness managersand others

Gene Serabyn



astronomers

planetary scientists physicistsmathematicianscomputer scientistsengineersartistseducatorspublic affairs officersbusiness managersand others

Diana Blaney



astronomers planetary scientists

physicistsmathematicianscomputer scientistsengineersartistseducatorspublic affairs officersbusiness managersand others

Ara Chutjian



astronomers planetary scientistsphysicists

mathematicianscomputer scientists

engineersartistseducatorspublic affairs officersbusiness managersand others

Jan & Paul Chodas



astronomers planetary scientistsphysicistsmathematicians

computer scientistsengineersartistseducatorspublic affairs officersbusiness managersand others

Jeanne M Holm



astronomers planetary scientistsphysicistsmathematicianscomputer scientistsengineers

artistseducatorspublic affairs officersbusiness managersand others

Sanjoy S Moorthy



astronomers planetary scientistsphysicistsmathematicianscomputer scientistsengineersartists

educatorspublic affairs officersbusiness managersand others

Leslie L Lowes



astronomers planetary scientistsphysicistsmathematicianscomputer scientistsengineersartistseducators

public affairs officersbusiness managersand others

Carolina Carnalla-Martinez



astronomers planetary scientistsphysicistsmathematicianscomputer scientistsengineersartistseducatorspublic affairs officers

business managersand others

Joanne Kennedy



What We Know

• About Planets

• About Planetary Systems

What We Want to Know

Knowledge and Ignorance of Extrasolar Planets

What we do know– Giant planet occurrence is high: ~7%– Mass distribution extends to near Earth’s mass– Eccentric orbits are common: scattering?– Many multiple systems of giant planets are known

What we don’t know– Existence of terrestrial planets

Are there low-mass planets in the ‘habitable zone’? Super-Earths certainly.

– Mass distribution of planets is incomplete and has strong selection effects

What about spectral type?Stellar age?Evolutionary state?

Planetary Systems: QuestionsStatistics of planetary systems – How common are

planetary systems?– Are certain star types

favored?– What is the distribution of

planetary systems in the Galaxy?

Characterizing planetary systems– What are the orbit radii?– Are the orbits circular or

eccentric?– Are multiple-planet

systems common??

For multiple planet systems– What is the typical mass

distribution of planets in a system?

– What is the typical radius distribution?

– Are the orbits co-planar?Must have astrometry to answer this

– Are the planets’ orbits stable?

How do we find out?

• About Planets

• About Planetary Systems

What We Want to Know

You can help us!

Small planet

Massive planet

Planets by Stellar Wobble

“The wobble effect”: our Solar System as seen at 10 pc distance

• 1 tick mark = 200 µas• Sun-Jupiter wobble = 500 µas • Sun-Earth wobble = 0.3 µas

Principle of Astrometric Planet Detection

How Much Wobble?

It can be measured with an accuracy of about 1 μas (quite a bit thinner than the line plotted here).

Ordinary Telescope – Optical, IR, Radio

An ordinary telescope collects electromagnetic radiation, forms an image which is then analyzed to determine the nature/position of the object in the field of view.

Telescope

diameter (D)

detector

Telescope Resolution Sensitivity

λ /D ∝D

λ = wavelength

Airy Disk

Michelson Stellar Interferometry

An interferometer combines the light from two or more small telescopes (Mersenne) to yield the angular resolution of a much larger telescope.

Interferometer

baseline (B)

Telescope (d) Telescope (d)Combiner &detector

Interferometer Resolution Sensitivity

λ /B ∝√ (2*d*B)

λ = wavelength

Fringe Pattern

SIM Lite could have made measurements precise enough to find Earths orbiting other stars.

But What Is a Habitable Planet?

Not too bigNot too small

Not too hot or too cold

A good planet is:

New spacecraft will be able to find planets similar in mass to Earth, at the “right distance” from their host stars. We can study them with advanced telescopes like...

Terrestrial Planet Finder – Interferometer (TPF-I)

International TPF-I / Darwin: Emma X-Array

Terrestrial Planet Finder – Coronagraph (TPF-C)

Images from3 Types of Coronagraph

Jupiter

Earth

42

Terrestrial Planet Finder – Occulter(TPF-O)

• Big telescope (planet is faint!)• Big occultor (few times size of

telescope)• Big separation (to see close to star)

NWD Starshade JWSTTarget Star

Planet

Blue (0.4-0.6 μm), Green (0.6-0.8 μm), Red (0.8-1.0 μm)

Color Gives a First Impression of a Planet

Solar system planetshave colors that label them by type.

Planet spectra

S. Seager

Vegetation as a Surface Biosignature

Visible photo

Near-infrared photo

TPF Investigations

The TPFs can distinguish between planets...

Searching for Other Earths

You can search for other Earths if you

• Want to explore new worlds.

• Read and learn as much as you can in the subject that interests you.

• Learn to share your ideas clearly in writing.

Searching for Other Earths

http://planetquest.jpl.nasa.gov/

and, for my Aliens vs. Editor blog,

http://planetquest.jpl.nasa.gov/ave

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Documents

NASA: How to Become a Planet Hunter: Careers in Space Science€¦ · Knowledge and Ignorance of Extrasolar Planets What we do know – Giant planet occurrence is high: ~7% – Mass