Detection of Extrasolar Planets ASTR 4: Life in the Universe

Outline Spectral Types Basic Geometry In-direct Methods –Astrometric Method –Radial Velocity (Doppler Spectroscopy) Method –Transit Method –Planetary Atmosphere Method –Pulsar Timing Method –Gravitational Microlensing Method Direct Methods –Direct Imaging –Interferometric Method –Coronagraphic Method

Spectral Types

Basic Geometry

Astrometric Method

Radial Velocity Method

"A Jupiter-Mass Companion to a Solar-Type Star", M. Mayor & D. Queloz, 1995, Nature 378, 355

8 Transits Planet crosses line of sight between observer and star and blocks a small amount of light from the star Different from occultation or eclipse Occult means to cover over or to hide Photometry Method of measuring the amount of light A light meter on a camera is a photometer Transit of Mercury in 2003 Transit Method

9 The relative change in brightness (  L/L) is equal to the relative areas (A planet /A star ) To measure 0.01% must get above the Earth’s atmosphere Method is robust but you must be patient: Require at least 3 transits, preferably 4 with same brightness change, duration and temporal separation (the first two establish a possible period, the third confirms it) Jupiter: 1% area of the Sun (1/100) Earth or Venus 0.01% area of the Sun (1/10,000) Transit Method - An Example

10 Not all planetary orbits are aligned along our line of sight to a star Diameter of Sun d* is about 0.01 AU. Diameter of Earth orbit D is 2 AU Random probability of detecting a Sun-Earth analog is about 0.5% So one needs to look at thousands of stars IF all have an Earth Geometry For Transit Probability

Transit Method – Light Curve

Transit Method - Light Curve Depth

Planetary Atmosphere Method

Gravitational Microlensing Method

The best fit light curve of the MACHO-97-BLG-41 microlensing event. The data consists of 356 MPS R- band observations from the Mt. Stromlo 1.9m telescope, 197 MACHO-R and 194 MACHO-V band observations from the Mt. Stromlo 1.3m telescope, 35 R-band observations from the CTIO 0.9m telescope, and 17 R-band observations from the Wise 1.0m telescope. The MACHO-R, MACHO-V, Wise-R, CTIO-R, and MPS data are plotted in red, blue, green, cyan, and magenta respectively. The tick interval for the inset figures is 1 day. 41/97blg41.html

Direct Imaging Method - Photometric Precision

Direct imaging of exo-planets is Hard: 10 Sun Earth

Differential Photometric Direct Imaging of a brown dwarf in infrared wavelength.

Other Direct Methods Interferometry –Infrared Interferometry –SIM (Space Interferometry Mission) Coronagraph –Visible Light Coronagraph –TPF (Terrestrial Planet Finder)

Infrared Interferometeric Image

SIM & TPF

Coronagraphic Imaging

Coronagraphic image of the Sun

Coronagraphic image of a brown dwarf; an object about 60 to 80 times the mass of Jupiter, orbiting less than 20 AU from its parent star. The star is removed by image processing to reveal the brown dwarf. (Keck and Gemini images)

26 Summary MethodYieldMass Limit Status Pulsar Timingm/M ;  LunarSuccessful (3) Radial Velocitym sini ;  UranusSuccessful (~100) Astrometrym ;  D s ; a Ground: TelescopeJupiterOngoing Ground: Interferometer<JupiterIn development Space: InterferometerUranusBeing studied Transit PhotometryA ;  sini=1 Ground Jupiter HD209458, OGLE TR-56? Space VenusPlanned Kepler, Edd. Reflection Photometry: albedo*A ;  SpaceSaturnPlanned Kepler, Edd. Microlensing: f(m,M,r,D s,D L ) Groundsub-UranusOn-going Direct Imagingalbedo*A ;  D s ; a ; M GroundSaturnBeing studied SpaceEarthBeing studied