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Extrasolar planet detection: Methods and limits

Extrasolar planet detection: Methods and limits. Ge/Ay133. How do you find a planet?. Look for it? Hard (as we’ll see)!. Only planets imaged are very young and far from their stars. Are such objects common or rare?. Duquennoy & Mayor (1991) - Binaries.

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Extrasolar planet detection: Methods and limits

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  1. Extrasolar planet detection: Methods and limits Ge/Ay133

  2. How do you find a planet? • Look for it? Hard (as we’ll see)! Only planets imaged are very young and far from their stars. Are such objects common or rare?

  3. Duquennoy & Mayor (1991) - Binaries • Where should you look?

  4. Eccentricities very different than the solar system:

  5. Secondary masses & planets?

  6. Spectral Energy Distributions (or, Blinded by the light!...)

  7. How do you find a planet? • Look for it? Hard! • Where should you look? Few AU? Further out easier… • Look for its affect on the star? (Indirect)

  8. Direct imaging of extrasolar planets: Marois et al. (2008) Kalas et al. (2008) • Initial systems consistent w/discovery space: • Young(ish) stars w/debris disks • Planets at fairly large radii (24/38/68 & 115 AU) • Both properties optimize detection potential.

  9. How do you find a planet? • Look for it? Hard! • Where should you look? Few AU? Further out easier… • Look for its affect on the star? (Indirect)

  10. 200 mas Astrometric displacement of the Sun due to Jupiter as seen from a distance of 10 pc (Current state of the art w/Keck AO = 200 mas, as of 2007)

  11. Discovery space for indirect methods: Radial velocity Astrometry (r=distance to the star)

  12. Radial velocity signature is distance independent (S/N is not!) First (written) proposal by Otto Struve,The Observatory 72, p. 199-200 (1952) 51 Peg announced in 1995 (PSR 1257+12 in 1992). .

  13. Spectroscopy with Echelles: Keck Photons have come a long way, don’t lose them! Echelle spectrometers in conjunction with large format arrays can provide R~30,000-100,000 spectra across the entire visible or near-IR range (l<5 mm, good for late type stars and brown dwarfs).

  14. Discovery space for indirect methods: Radial velocity Astrometry

  15. Other distance independent tracers? TRANSITS Technique proposed in 1952, HD 209458 detected in 2000. 100’s now with the first CoRoT and Kepler results.

  16. Transit photometry from space: Kepler!

  17. Routes to Earth-like planets?

  18. Microlensing II: Best geometry uses stars at a few kpc against the Galactic Bulge. 5.5 MEarth planet at 2.6 AU around a M-dwarf (0.22 M) primary at 6.6 ± 1.0 kpc. J.-P. Beaulieu et al. Nature 439, 437-440 (26Jan2006)

  19. Astrometry? Hard w/single apertures, but moving forward, ultimately to imaging. Keck LGS-AO image, can now achieve ~200 mas precision over short timescales. HST worse. ACS + Coronograph (HD 141569) Artist’s conception, TPF-C (coronograph).

  20. Think about interferometry?

  21. Aperture Diffraction Pattern

  22. Radio arrays can give mas precision (non-thermal):

  23. In the optical, difficult to maintain strict instrument stability, so use “dual star” astrometry. Large apertures are needed to get enough background stars nearby.

  24. Nulling: Use the fringes to suppress the central star. First successful tests with Keck in 2007… Jupiter simulation at 10 pc.

  25. Nulling can also be used with single apertures… Vortex coronograph image, using 1.5m section of the Hale telescope. Discovery image, 10.4m Keck telescope

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