Survey
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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?