Post on 23-Feb-2016
description
IntroductionFinding Planets• Pulsar Timing• Astrometry• Polarimetry• Direct Imaging• Transit Method• Radial VelocitySelecting Planets• Recap• What else do we want to know?Proposed Plan
Outline
Pulsar Timing MethodFirst exoplanet confirmation! (1992)Poor candidates for life
Wolszczan and Frail, 1992
• 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
Astrometry
• 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
Polarimetry
University of Hertfordshire
Land-Based Direct ImagingTechnological Aspects• Larger Mirrors• Atmospheric Distortions• Adaptive Optics (e.g. Keck)• Glare from host star • Coronograph (e.g. Gemini Planetary Imager)• > 5 AU• Optical and Near IR spectraResultsPotentially useful for finding life
Keck II w/laser guide (CASA)
Simulation of Coronograph, (GPI)
• 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
Direct Imaging – Hubble Telescope
http://www.youtube.com/watch?v=HAWMa_YEuKI
(NASA)
Dip in flux ~10^-5Space-basedMass, period• T, habitability
Transit Photometry Method
(NASA)
http://www.youtube.com/watch?v=vjdxJQj4QHY
Transit Method (Kepler Mission)Looking for terrestrial planets in habitable zonesLaunched 3/7/2009Solar neighborhood-like regionOrbit:• Earth-trailing, (372.5 days)•Off-ecliptic6 year mission• 3 transits for significanceFollow-up ObservingGood start to look for life Kepler (NASA)
2321 candidates around 1790 stars61 confirmed
(2/27/12)
2321 candidates around 1790 stars61 confirmed
(2/27/12)
Blue are habitable candidates48 canidates1 confirmed (Kepler 22b)
• 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 (Doppler Spectroscopy)
• 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
Radial Velocity - HARPS
msnbc - Artist rendition of sunset on super-Earth Gliese 667 Cc
Open QuestionsRocky or gas giantAtmosphereOrbit stabilityPresence of:• Water• Methane• Carbon Dioxide• Plate Tectonics• Satellite(s)
• Astronomer median annual wage: $95,500
• Mission cost: $1 mil per year
• 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
Proposed Plan