1. New Worlds: Detection of Exoplanet systems
Bryce Carande October 29, 2010 Astrophysics 591

2. Exoplanets: Outline Relation to Decadal survey
How do we find Exoplanets?
Methods of detection
Useful Observatories (current and forthcoming)
Spotlight: Gleise 581 system
History of discoveries
Mayor 2009 (4-planet solution)
Vogt 2010 (6-planet solution)
Gleise 581g
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3. Exoplanet science
Burgeoning field: drastically advanced in the last decade
Discoveries often limited only by observation time
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4. Decadal survey for Astronomy and Astrophysics
3 Science objectives:
Cosmic Dawn, New Worlds, Physics of the Universe
3 scales of space missions to accomplish objectives:
Large,
medium,
small
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8. Detection methods Radial Velocity Transit Direct Imaging
Interferometry
Gravitational Lensing
Astrometry
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9. Radial Velocity Method
Measure Doppler shift of light due to star’s perturbed motion
Can only detect motion along radial axis i
Orbital plane of system
Planet with mass m
Effect of planet on our observed Radial Velocity:
= m sin(i)
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10. Observatories for Exoplanets
Current
New
Earth-based
Keck (Hires)
Ten meter telescope or
Giant Magellan Telescope
La Silla (3.6m)
European Extremely Large Telescope
Space-based
Hubble
JWST
Kepler
Darwin
Corot
Terrestrial Planet Finder
* Very incomplete
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11. Gleise 581: The star M-dwarf type star (.31 solar mass)
20.3 light years from Earth
Sub-solar Metallicity (-.25 to -.33)
Relatively ‘quiet’ star
No indications of strong B-field
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12. Gleise 581’s history of planets
Year
Lead Author
Group
Data set
Planets Discovered
Notes
2005
Bonfils
HARPS 20
B (15.7 M⊕)
Hot Neptune
2007
Udry 50
C (5.03 M⊕)
D (7.7 M⊕)
C: lowest mass to date, “most Earthlike”, inner edge of habitable zone
Selsis, others -
C: likely too hot for HZ
D: could host liquid water given thick greenhouse atmosphere
2009
Mayor
119
E (1.9 M⊕)
D: orbit revised to be closer; now within HZ
2010
Vogt
HIRES
F (7.0 M⊕)
G* (3.1 M⊕)
Confirms previous results
G: Terrestrial planet in HZ!
*unconfirmed
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13. Equipment: ESO 3.6m telescope in La Silla Observatory, Chile
The HARPS search for southern extra-solar planets XVIII. An Earth-mass planet in the GJ 581 planetary system (2009) M. Mayor1, X. Bonfils2,3, T. Forveille2, X. Delfosse2, S. Udry1, J.-L. Bertaux4, H. Beust2, F. Bouchy5, C. Lovis1, F. Pepe1, C. Perrier2, D. Queloz1, and N. C. Santos1,6
Equipment: ESO 3.6m telescope in La Silla Observatory, Chile
HARPS = High accuracy radial velocity planet searcher
Discovered 75 exoplanets during original 5 year mission (out of 400 known)
- Bimodal distribution of planet masses: super earths (<10 Me) and gas giants (>30 Me)
Focused on nearby M-dwarf stars
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14. The HARPS search for southern extra-solar planets XVIII
The HARPS search for southern extra-solar planets XVIII. An Earth-mass planet in the GJ 581 planetary system
Complete Signal
corrected for b
corrected for b,c
corrected for b,c,d
corrected for all
e (3.15d)
b (5.63d)
c (12.9d) e
59d? d? 82d? d:
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15. The HARPS search for southern extra-solar planets XVIII
The HARPS search for southern extra-solar planets XVIII. An Earth-mass planet in the GJ 581 planetary system
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16. Fit 6 planets to data Equipment: Keck telescope with HIRES instrument
The Lick-Carnegie Exoplanet Survey: A 3.1 M⊕ Planet in the Habitable Zone of the Nearby M3V Star Gliese 581 Steven S. Vogt1, R. Paul Butler2, E. J. Rivera1, N. Haghighipour3, Gregory W. Henry4, and Michael H. Williamson4
Equipment: Keck telescope with HIRES instrument
122 RV measurements over 11 years
Combined measurements with HARPS data
Fit 6 planets to data
Confirmed previous planets; added 2 more
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17. Periodogram Also did reverse process: Start with 6-planet solution
Re-combine each planet back into data set
See if discernable peaks arise
-> HARPS data alone insufficient to detect g
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18. Combined data sets
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20. Implications for η⊕ Fraction of planets within a habitable zone
581g makes number 2
302 dwarf type stars within 10pc
Only 10 of these have more than 200 RV observations (incompleteness factor)
η⊕ = (2 / 302)*(302/10) = 20%
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21. Questions?