The NASA-UC Eta-Earth Survey: A Systematic Search for Low-mass Planets From Keck Observatory - Andrew Howard - Townes Post-doctoral Fellow, UC Berkeley HD 7924b Collaborators Geoff Marcy Debra Fischer John Johnson Jason Wright Katie Peek Greg Henry Matt Giguere Howard Isaacson Julien Spronck Kevin Apps Jeff Valenti Jay Anderson Nikolai Piskunov David Bernat Mike Endl Bill Cochran
Outline RV Planet Searches Improving Doppler Precision Population Synthesis Planet Formation Models Eta-Earth Survey Future Directions
Doppler Monitoring Begun: 1987 Duration: 20 Years + Jupiter Analogs? 1500 FGKM M.S. Stars 22 Years (7 AU) Lick 13 Years (5 AU) Keck 11 Years (5.5 AU) Anglo-Aus. Tel.
California Planet Search CPS Planet Searches: Eta-Earth Survey Long-term survey Kepler follow-up Sub-giant Search M dwarf Search M2K Search Rossiter Measurements HAT Follow-up HAT Follow-up Rossiter Long-term Eta-Earth Sub-giant Kepler Measurements Followup Survey Search M dwarf Planet Search M2K SearchWASP-14 New Search led by Debra Fischer Focus on K-stars and M-stars First detections soon! HAT-P-13b,c Spin-orbit Misalignment
Doppler Wobble Nearly all exoplanets detected (or confirmed) by Doppler measurements 1 m s -1 10-3 pixel
Wavelength Calibration 8 Significant Digits Echelle Spectrometer Resolution: 60,000 Iodine Abs. Cell Superimpose I 2 lines Wavelength Calib. PSF Determination
Stellar Spectrum: Echelle 4000 Pixels on CCD 2 m/s 0.001 pixel (80 Si atoms) l Calib: 8 sig. fig. (v/c).
Improving Velocity Precision - All Stars New Pipeline: by John Johnson, also Debra Fischer for Lick data Re-compute 2004-present velocities: equal or better performance on standard stars l DOP I obs (l) k[t I 2 (l) I S (l l)] PSF Observed Iodine Intrinsic Stellar Point Spread Spectrum Transmission Spectrum (shifted) Function
Fiber Scrambler - Lick Observatory
Standard Stars - 1.5-2.5 m/s
How Common are Low-mass Planets? Burning Debate! 38% - 58%!! Theory predicts few super-earths and Neptunes in short-period orbits Swiss group claims that 30% ± 10% of GK dwarfs have rocky or Neptune planets inward of 50-day orbits Our initial results show relatively few Super-Earths and Neptunes
Ida-Lin Planet Formation Theory Simulate core-accretion process Start with rocky planetesimals and gas All them to grow, migrate, and accrete gas Include effects such as gas-planetesimal interactions and ice condensation Compare final planet distribution with observations
RV Observations Ida/Lin Theory Ida & Lin 2009, ApJ, 685, 584
Extrasolar Planet Phase Space Current harvest of ~350 planets (RV): empirical constraints on planetary system formation. Jupiter & Neptune appear to be the tip of the planetary iceberg. Simulations from Ida & Lin
Ida & Lin 2009, ApJ, 685, 584
Mordasini, Alibert, & Benz, A&A, 501, 1139
Mordasini, Alibert, & Benz, A&A, 501, 1139
Mordasini, Alibert, & Benz, A&A, 501, 1139
Gliese 876: 3-Planet Model Rivera et al. 2005
Velocity GJ 876 d Velocity Residuals to 2-Planet Fit Period = 1.94 d M sini = 5.9 M Earth For i = 50 deg, M PL = 7.5 M Earth Orbital Phase
NASA-UC Eta-Earth Program RV survey of 238 nearby GKM dwarfs Search for low-mass planets (Msini = 3-30 MEarth) Constrain population of low-mass planets and planet formation theory 39% G stars 33% K stars 28% M stars Eta-Earth stars Hipparcos (d < 50 pc) Statistically unbiased (nearly) stellar population: V < 11 distance < 25 pc log R HK < -4.7 (inactive)
Typical non-detection 1 high-cadence run 20+ observations over 4 years
Progress on on Eta-Earth Sample (2) ~80% of stars have 20+ observations ~80% of stars have 1 high-cadence run ~30 low-mass candidates being followed-up Progress on 20+ obs/star Done Progress on 1 high-cadence run/star Done
HD 7924b - Super-Earth Detection Star: HD 7924 (K0V) Planet: M sin i = 9.3 M Earth P = 5.398 d e = 0.17 (consistent with circular) Howard et al. 2009, ApJ, 696, 75
Precision of Eta-Earth Observations Velocity RMS of Eta-Earth stars Limited by: Stellar jitter Photon noise Wavelength reference stability Other instrumental effects (guiding, etc.)
RV Precision/Noise Keck/HIRES HARPS Eta-Earth Survey stars GKM Chromospherically quiet ~10-100 observations each Mayor and Udry, 2008, Phys. Scr. T130, 014010
Properties of Super-Earths and Host Stars Super-Earths Hosts: Low Mass Metal poor (controversial) Super-Earth Planets: Multi-planet systems Excluding: GJ 581e Corot-7 Microlensing planets Pulsar planets Howard et al. 2009, ApJ, 696, 75
Known Planets in Eta-Earth Survey 37 planets orbiting 23 stars (out of 238 stars in Eta-Earth Survey) Known Eta-Earth Planets By Mass: 18 Jupiters 7 Saturns 6 Neptunes 6 Super-Earths
Next Steps for Eta-Earth Survey Finish survey observations (~6 months) Intensive follow-up observations of best low-mass candidates Announce more super-earths and Neptunes! Transit searches for announced and candidate low-mass planets Statistical study of low-mass / short-period exoplanets in Eta-Earth Survey
Dedicated Planet Finder Telescope 365 nights/year Nightly Observations Allow Detection of Planets of ANY Orbital period: Days, Weeks, Months Wobble can be detected Over and Over: Detect smallest wobbles Caused by smallest planets.
Groundbreaking Sept 15, 2005
APF Telescope
Under Construction: Robotic Telescope to Search for Earth-Like Planets 2.4 meters
The APF Spectrometer Spectrometer optimized for ultra-precision Doppler Shifts. Athermalized optical train High efficiency (35%) l/ l = 100,000 (for 1 arcsec slit) 1 meter/sec velocity precision Cost: $1.2 million Designed by Steve Vogt
APF Spectrometer First Light!
Simulation: New Telescope During 1/2 Year Hypothetical Planet: 10 Earth-Masses Orbital Period = 50 days * Temp = 80 C Time (Days) 50.29 days Peak Power Power of the Dedicated Telescope: Repeated Orbital Cycles Confirm Planet
Simulation: New Telescope During 1/2 Year Hypothetical Planet: 2 Earth-Masses Power of a Dedicated Telescope: Repeated Orbital Cycles Improves Detectability Peak Power * Temp = 80 C
Questions?