Extrasolar planets Emre Işık (MPS, Lindau) S 3 lecture Origin of solar systems 14 February 2006

Outline Planet detection methods –Methodology –Some recent results Statistical properties of exoplanets Future prospects

Struve, O Obs., 870, 199

Detection techniques I Precise stellar radial velocities to observer N. Strobel to observer N. Strobel

Detection techniques II Transit photometry  a = (P orb R  ) /  t  f / f  = (R p / R  ) 2

Detection techniques II Transit photometry Advantages Easy (if automated!), small telescopes with good sites/detectors Possibility to detect low-mass planets, especially from space (Kepler mission, 2008) Disadvantages Transit probability low; simultaneous observations of many stars Confusion with starspots, multiple stars Planets around binary stars Deeg (1998) Reflection effect

HST light curve of HD b Brown et al. (2001) Stellar radius and limb-darkening profile Planet's mass and radius No rings around the planet No moons with M > 3 M E (repeated obs.)

Detection techniques III Microlensing

Detection techniques III Microlensing events OGLE 2003-BLG-235/MOA 2003-BLG-53 Discovered planet: 1.5 M 3 AU Bond et al. 2004, Astroph. J. Letters, 606, L155

Detection techniques III Microlensing events Discovery of a Cool Planet of 5.5 Earth Masses. OGLE-2005-BLG-390 Beaulieu et al., 2006, Nature, 439, 437Nature, 439, 437 Discovered planet: 5.5 M 2.6 AU

Detection techniques IV Astrometry “Celestial” motion of the Sun due mainly to Jupiter & Saturn, as seen from 33 light years away…

Astrometry A Jupiter analog orbiting 5 AU from a solar-type star produces an astrometric amplitude of 0.5 milliarcsec (mas). A star with planet close to (about 1 arcmin) to a star without planet is needed. Direct, short CCD exposure at Palomar 5m and Keck telescopes may yield 0.1 mas. Palomar test-bed interferometer yields μas, VLTI should allow 20 μas. Space missions may do better as interference from terrestrial atmosphere is eliminated. As of 1998, no object has been found. Technique is in its infancy. Big telescope resources are needed.

Detection techniques V Direct imaging !

Visible lightInfrared light

Name: 2M1207 b Msini: 5 ± 1 M J Radius:1.5 R J Temperature1240 ± 60 K Semi-major axis: (projected dist.) ~ 55 AU Orbital period: > 2450 yr Mass (star/M_sun): NACO/VLT image, Chauvin et al Detection techniques V Direct imaging !

Substellar companion to GQ Lupi IR image (NACO/VLT) GQ Lupi (A) orbited by a planet (b) at a distance of ~20xJupiter-Sun. GQ Lupi: 400 ly, 0.7 M  Mass: 1-42 M J

Detection techniques VI [reflection/absorption] spectroscopy

Caution: “planet occurrence” is biased by RV sensitivity!

Properties of the detected planets Lineweaver & Grether 2003

Properties of the detected planets Lineweaver & Grether 2003

Extrapolations Lineweaver & Grether 2003

Evolutionary models Different assumptions on the inhibition of cooling by irradiation from the parent star, and the planet's internal structure (Burrows et al. [2000], Bodenheimer et al. [2001] and Guillot and Showman [2002]) Fig.: Collier Cameron (2002)

The future: Future of future: CO 2 O3O3