Transcript Finding Planets - Department of Earth and Planetary Sciences

Planet Survey Mission
Tim Healy
Tony Perry
Outline
Introduction
Finding Planets
• Pulsar Timing
• Astrometry
• Polarimetry
• Direct Imaging
• Transit Method
• Radial Velocity
Selecting Planets
• Recap
• What else do we want to know?
Proposed Plan
Introduction
(NASA)
Finding Planets
Pulsar Timing Method
First exoplanet confirmation! (1992)
Poor candidates for life
Wolszczan and Frail, 1992
Astrometry
•
Precisely measure a star’s position over
time
•
Mutual center of mass (barycenter)
•
Successful in characterizing binary star
systems
•
Inaccurate claims of ‘unseen companions’
•
Not useful unless planet is massive
•
Good as a complementary technique
Polarimetry
University of Hertfordshire
•
Un-polarized starlight
•
When the light reflects of a planet’s
atmosphere, it becomes polarized by
interacting with the molecules in the
atmosphere
•
Analyze light in search of polarization
•
No planets found using this method
Land-Based Direct Imaging
Technological Aspects
• Larger Mirrors
• Atmospheric Distortions
• Adaptive Optics (e.g. Keck)
• Glare from host star
• Coronograph (e.g. Gemini Planetary Imager)
Simulation of Coronograph, (GPI)
• > 5 AU
• Optical and Near IR spectra
Results
Potentially useful for finding life
Keck II w/laser guide (CASA)
Direct Imaging – Hubble Telescope
•
Difficult to directly detect planets
(extremely faint light sources)
•
Low Earth orbit in 1990
•
View the near ultraviolet, visible, and
near infrared
•
Outside the distortion of Earth’s
atmosphere (no background light)
•
•
Ultra-Deep Field image
2006 - Sagittarius Window Eclipsing
Extrasolar Planet Search (SWEEPS)
•
16 extrasolar candidate planets
discovered
•
When extrapolated, strong evidence
of about six billion Jupiter-sized
planets
(NASA)
http://www.youtube.com/watch?v=HAWMa_YEuKI
Transit Photometry Method
Dip in flux ~10^-5
Space-based
Mass, period
• T, habitability
(NASA)
http://www.youtube.com/watch?v=vjdxJQj4QHY
Transit Method (Kepler Mission)
Looking for terrestrial planets in habitable zones
Launched 3/7/2009
Solar neighborhood-like region
Orbit:
• Earth-trailing, (372.5 days)
• Off-ecliptic
6 year mission
• 3 transits for significance
Follow-up Observing
Good start to look for life
Kepler (NASA)
2321 candidates around 1790 stars
61 confirmed
(2/27/12)
Blue are habitable candidates
48 canidates
1 confirmed (Kepler 22b)
Radial Velocity (Doppler Spectroscopy)
•
Similar to Astrometry
•
Radial velocity calculated from
displacement in parent star’s spectral
lines due to the Doppler effect
•
Modern spectrometers can detect
velocity variations 1 m/s or less
•
•
High Accuracy Radial Velocity Planet
Searcher (HARPS)
•
Most productive planet hunting
technique by far
When used in combination with the
Transit Method, the planet’s true mass
can be estimated
Radial Velocity - HARPS
• Surveyed 102 red dwarfs
•
Thought to make up ~80% of the stars in our galaxy
• 40% of all red dwarf stars have a super-Earth orbiting the habitable zone
• Estimated tens of billions of these planets exist within the Milky Way
• Stellar eruptions, flares
msnbc - Artist rendition of sunset on super-Earth Gliese 667 Cc
Selecting Planets
Compiled Results
Catalog of planets (mass, period, host star)
Lunine et al., 2009
Open Questions
Rocky or gas giant
Atmosphere
Orbit stability
Presence of:
• Water
• Methane
• Carbon Dioxide
• Plate Tectonics
• Satellite(s)
Proposed Plan
Proposed Plan
•
Utilize two most productive planet
searching techniques
•
Transit Method (Kepler)
•
Radial Velocity (Doppler)
•
Kepler - mission cost for entire life
cycle is ~$600 million
•
Doppler - ESO 3.6 m telescope cost is
$41.7 million (HAPRS was installed in
2002 on this telescope)
•
James Webb Space Telescope – 2018
launch date
•
ELT, first light 2020s
•
Astronomer median annual wage:
$95,500
•
Mission cost:
$1 mil
per year
Questions?