Overview on
Extra Solar Planets
Rahul I. Patel
PHY 599 – Grad Seminar
Oct. 18th 2010
OUTLINE
• Motivation
• Current Theory
• Methods of Detection:
– Radial Velocity
– Direct Imaging
– Others
• Results
– Detected Exo-Planets
• Modified Theory
• Future
• Conclusion
Rahul I. Patel : Extrasolar Planets
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MOTIVATION
MOTIVATION : I, Human
• Copernicus and Bruno
(16th Century)
The Heliocentric Model
•1995: “First” exoplanet 
around 51 Pegasi
• < 10 yrs, instrument
precision increased
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MOTIVATION: For Science!
• Advancement in observation technology  possibility
of detecting planets
- That hold life?
• Planet formation process
• Solar system evolution
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Old Theory
PFT: Nebular Hypothesis
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METHODS
OF
DETECTION
MOD: Radial Velocity
• Doppler shift of stellar spectral
lines  COM orbit
• Detectors: HARPS, HIRES
• High S/N ratio
• Range: Dmax= ~160 Ly
• Observations may take years
due to SMA distance
• Estimate planet minimum mass
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Planets of the RV : HD 69830
• 3 planets around HD 69830 ( 0.86 M☉ )
• HD 69830: d = 12.6 pc, ST = K0V, V = 5.95
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Planets of the RV : Gliese 581
•
Gliese 581: M3V star: Red Dwarf
@ 20 Ly
•
RV survey over 15 years (HIRES,
HARPS) 6 companions
•
Gliese 581g  min mass: 3.1 M⊕
@ 0.146 AU, P = 36.6 days
•
Within habitable zone, Test ~
228K
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Planets of the RV : Gliese 581
• b,c,d,e  Confirmed
• f, g can’t be confirmed
by separate team using
HARPS data
• Signal amplitude of ‘g’
very low  level of
measurement noise
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MOD: DIRECT IMAGING
• Actually SEE orbiting planets  not indirect
• Problem: Host Star
• Need >MJ , Large SMA distance, and Extremely hot for IR
radiation - HIGH CONTRAST
• Problem:
– Diffracted Light: optical diffraction, imperfect optics, residual
wave front error
• New Methods:
Coronagraphs
Adaptive Optics
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DIRECT IMAGING: Coronagraphs
• Device to block light to resolve nearby objects
• 1930  Bernard Lyot
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DIRECT IMAGING: Adaptive Optics
The binary star IW Tau is revealed through adaptive optics. The
stars have a 0.3” separation. The images were taken by Chas
Beichman and Angelle Tanner of JPL.
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Planets of Direct Imaging
Fomalhaut b
• 2.1 M☉, 1-3E7 yr, 8,751K, A3V
• 11/13/08 1st directly imaged
planet in V band (HST)
• 0.054 - 3.0 MJ
• 115 AU, T = 872 yrs
• e = 0.11
HR 8799 b,c,d
• HR 8799a: 1.5 M☉, ~60Myr, 39 pc, F0V
• Debris disk : 3 planets
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Other Methods…
• Transit
• Astrometry
Transit
• Microlensing
Astrometry
• Pulsar Timing
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Best Case…
• Combine multiple methods for
meaningful analysis:
- RV : Mass
- Transit: Radius  Density, Transit Spectroscopy
- Direct Imaging  Photometry  Temperature 
Atmospheric composition
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RESULTS
RESULTS
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RESULTS
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RESULTS
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Alternate Planet
Formation
Theories
PFT: Exo-Planets Shake Things Up
• Giant exo-planet (MJ) detected with T :[1.2 days, ~10 yrs]
- MJ planets w/in Frost Line
• Comet like eccentricities of some planets
• Some planets as massive as 15 MJ  Heresy to call them planets?
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PFT: Alternate Models I
• Core Accretion Model:
– Solid core from accreting planetismals
– Becomes massive enough to bind gas into envelope
– After critical value, envelope starts to contract, increasing
gas accretion rate, raising radiative energy loss  rapid
buildup of massive envelope
– Need critical core mass before protoplanetary disk
disappears  ~1-10 Myr
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PFT: Alternate Models II
• Direct Collapse Model
- Giant planets form from gravitational fragmentation,
collapse of disk in timed intervals
• Migration
- time scales short  should fall into host star
- Since Jupiter mass planets observed, migration model
incomplete
- slowed down due to : tidal interactions with host star
(might also cause high eccentricity)
- does not explain giants at intermediate distances, or why
Jupiter remains at 5 AU
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Future Work
FUTURE WORK: Extreme AO
• Find planets in Debris Disks: High contrast ratio
• Keck NGAO (10 m)
• Palm 3000 at Palomar(5 m)  1st Extreme AO (2011)
(JPL and Caltech)
– Precision near-IR photometry and astrometry
– High contrast imaging and high sensitivity faint-object visible light
imaging.
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FUTURE WORK: JWST
• Thermal IR
5–25 µm
• Warm Planets
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CONCLUSION
• Several methods of detection
– Transit, Radial Velocity Survey, Astrometry,
– Direct Imaging
• Odd ball planets all over the place
• No obvious pattern
• Reformulation of planetary formation
• Future Missions: KEPLER, JSWT, Palomar PALM 3000
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References
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Lovis, C. et. al. An extrasolar planetary system with three Neptune-mass planets. Nature 441,
305-309 (18 May 2006).
Marcy, G. et. al. Observed Properties of Exoplanets: Masses, Orbits, and Metallicities. Progress
of Theoretical Physics Supplelement 158 (2005).
Mordasini, C. et. al. Extrasolar Planet Population Synthesis I. Method, formation tracks, and
mass-distance distribution. A&A 501, 1139–1160 (2009)
Santos, N. et. al. Extrasolar Planets: Constraints for Planet Formation Models. Science 310, 251
(2005).
Udry, S. et. al. Statistical properties of exoplanets I. The period distribution: constraints for the
migration scenario. A&A 407, 1 (2003) 369-376 .
http://en.wikipedia.org/wiki/List_of_extrasolar_planets
http://en.wikipedia.org/wiki/Methods_of_detecting_extrasolar_planets#Transit_method
http://www.astro.psu.edu/users/niel/astro1/slideshows/class43/slides-43.html
S. Hinkley, B. Oppenheimer, High contrast observations in Optical and Infrared Astronomy. Annu
Rev. Astro Astrophysics, 2009.
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