Survey
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What have (pre-Kepler) radial velocity surveys told us about exo-planetary science? Ch/Ge128 We have dreamed of extrasolar planets for a long time, … English engraving 1798 (and Physics Today 4/2004). Now we can detect them! Jupiter mass planets from <0.05 to >50 astronomical units! C. Marois (2010) Kepler is pushing well into the hot Neptune & super-Earth regime. How do we do this? Discovery space for indirect methods: Radial velocity Astrometry (r=distance to the star) Mayor, M. & Queloz, D. 1995, Nature, 378, 355 Udry, S. et al. 2002, A&A, 390, 26 Jovian planets througout the 0.05-5 AU region. And… Updated plots follow. No strong preference for orbital distances… …except for a “pile up” of hot Jupiters at P~3 days. Planetary characteristics? Some trend in M versus R (bias?), but beyond 0.05-0.1 AU, little preference for low eccentricities: Eccentricities. II. Short Period Circularization Even with incompleteness, strong preference for ~Jovian mass: Stars are different, turnover at low mass! Orion IMF “The brown dwarf desert”? Does this tell us that stars and planets form differently? Is there an eccentricity preference w/mass? Not really… Marcy, G. et al. 2005, astro-ph/0505003 Is there an eccentricity preference w/mass? Not really, part II… ? Butler, R.P. et al. 2006, ApJ, 646, 505 Another clue as to formation: Planet formation efficiency correlates strongly with metallicity! Fischer, D.A. & Valenti, J. 2005, ApJ, 622, 1102 What about planet formation efficiency & stellar mass? Radial velocity surveys mostly focused on Sun-like stars. Why? Active Chromospheres Low-contrast Lines Johnson, J.A et al. 2007, ApJ, 665, 785 What about planet formation efficiency & stellar mass? Clever idea for higher mass A stars: Look at older systems that have evolved off the main sequence. Johnson, J.A et al. 2007, ApJ, 665, 785 What about planet formation efficiency & stellar mass? M4 – K7 K5 – F8 F5 - A5 Two preliminary findings (that are being tested with larger surveys): 1. Planet formation efficiency increases w/mass. 2. The proportion of hot Jupiters decreases w/mass (not observational bias). Johnson, J.A et al. 2007, ApJ, 665, 785 What about planetary multiplicity? Complex doppler patterns: Summary of several of the known multiple planetary systems: Marcy, G. et al. 2005, astro-ph/0505003 A super earth & GJ 876? Rivera, E.J. et al. 2005, (see class web site) GJ 876 orbits evolve with time (expected w/mutual perturbations)! What about other systems? Rivera, E.J. et al. 2005, (see class web site) A habitable super-Earth? The GJ 581(M3V) system: Vogt, S.S. et al. 2010, (arXiv:1009.5733v1) HD 168443 b: 7.2 Mj 58 days c: 17 Mj 1739 days =1/29.98 ?! 30:1? HD 12661 b: 2.3 Mj 263 days c: 1.6 Mj 1444 days =1/5.5 11:2? 47 U Ma b: 2.5 Mj 1089 days c: 0.76 Mj 2594 days =1/2.4 Gleise 876 b: 1.89 Mj 61 days c: 0.56 Mj 30 days HD 37124 b: 0.75 Mj 152 d c: 1.2 Mj 1495 d ups And b: 0.69 Mj 4.6 d c: 1.9 Mj 241.5 d d: 3.75 Mj 1284 d HD 82943 b: 1.63 Mj 444 d c: 0.88 222 d 55 Cnc b: .84 Mj 14.6 d c: 0.21 Mj 44.3 d d: 4 Mj 5360 d 3:1! What we know: - ~1% of solar-type stars have Hot Jupiters -~7% of solar-type stars have >Mj planets in the “terrestrial planet” region. Extrapolation of current incompeteness suggests >12% w/planets @ <20 AU. - multiple planetary systems are ~common - planetary resonances are ~common What can explain these properties? Theory Disk-star- and protoplanet interactions lead to migration while the gas is present. Coreaccretion? 1 AU at 140 pc subtends 0.’’007. Simulation G. Bryden, JPL Thus, need to study objects in this phase… Jupiter (5 AU): V_doppler = 13 m/s V_orbit = 13 km/s Core-accretion models can now be compared to observations: Data Tests? Planets versus metallicity: Ida, S. & Lin, D. 2004, ApJ, 616, 567 Observed in open circles. Early disk models held that eccentricities were DAMPED. Not so fast… Goldreich, P. & Sari, R. 2003, ApJ, 585, 1024 Goldreich & Sari 2005 Need an initial e~0.01.