1 / 90

Exoplanet Detection Techniques II GUASA 12/10/2013 Prof. Sara Seager MIT

Exoplanet Detection Techniques II GUASA 12/10/2013 Prof. Sara Seager MIT. Exoplanet Detection Techniques II. Planet Detection Techniques in More Detail Direct Imaging Microlensing Astrometry. Direct Imaging Lecture Contents. Direct Imaging Planet and Star Spatial Separation

Download Presentation

Exoplanet Detection Techniques II GUASA 12/10/2013 Prof. Sara Seager MIT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Exoplanet Detection Techniques II GUASA 12/10/2013 Prof. Sara Seager MIT

  2. Exoplanet Detection Techniques II • Planet Detection Techniques in More Detail • Direct Imaging • Microlensing • Astrometry

  3. Direct Imaging Lecture Contents • Direct Imaging • Planet and Star Spatial Separation • Adaptive Optics • Direct Imaged Candidates • What is Being Measured? • Planet-Star Flux Ratios

  4.  National Geographic used with permission

  5. Direct Imaging • Number 1 requirement is to spatially separate planet and star

  6. Direct Imaging • Number 2 requirement is to literally block out the glare of the star

  7. Diffraction • Light from a point source passes through a small circular aperture, it does not produce a bright dot as an image, but rather a diffuse circular disc known as Airy's disc • The disk is surrounded by much fainter concentric circular rings.

  8. Diffraction • Light from a point source passes through a small circular aperture, it does not produce a bright dot as an image, but rather a diffuse circular disc known as Airy's disc • The disk is surrounded by much fainter concentric circular rings.

  9. Spatial Resolution • Rayleigh criterion: the minimum resolvable angular separation of the two objects • Single slit • Circular aperture •  is the wavelength of light, D is the aperture diameter

  10. Ground-Based Limitations • Turbulence in the atmosphere blurs mixes up photon paths through the atmosphere and blurs images

  11. Ground-Based Limitations • Turbulence in the atmosphere blurs mixes up photon paths through the atmosphere and blurs images • Adaptive optics can correct for this! • http://planetquest.jpl.nasa.gov/Planet_Quest-movies/AO_quickTime.html

  12. Direct Imaging Lecture Contents • Direct Imaging • Planet and Star Spatial Separation • Adaptive Optics • Direct Imaged Planet Candidates • What is Being Measured? • Planet-Star Flux Ratios • Direct Imaging Techniques for Earths

  13. Direct Imaged Planet Candidates Note this plot is somewhat out of date Based on data compiled by J. Schneider

  14. TMR-1 NASA/Terebey

  15. This is a discovery image of planet HD 106906 b in thermal infrared light from MagAO/Clio2, processed to remove the bright light from its host star, HD 106906 A. The planet is more than 20 times farther away from its star than Neptune is from our Sun. AU stands for Astronomical Unit, the average distance of the Earth and the Sun. (Image: Vanessa Bailey)

  16. HR 8799 See also: http://www.space.com/20231-giant-exoplanets-hr-8799-atmosphere-infographic.html

  17. 2M1207

  18. Gl 229 a NASA/Kulkarni, Golimowsk)

  19. 55 Cnc Oppenheimer

  20. GQ Lup

  21. AB Pic

  22. SCR 1845-6357 Biller et al. 2006

  23. SCR 1845-6357 9 - 65 MJup (likely T-dwarf) Very close to Earth: 3.85 pc ~4.5 AU from primary Biller et al. 2006

  24. CT Cha Schmidt et al. 2008

  25. CT Cha 17±6 MJup 2.2±0.8 RJup 165±30 pc ~440 AU T=2600±250 K Background star Star: classical T Tauri (0.9-3 Myr) Schmidt et al. 2008

  26. 1RXS J160929.1-210524 Lafreniere et al. 2008

  27. 1RXS J160929.1-210524 330 AU 150 pc T=1800±200 K M=8 (+4 -1) MJup Young solar mass star (5 Myr) Lafreniere et al. 2008

  28. Direct Imaged Planet Candidates This table is incomplete. Let’s look at a table online …

  29. Direct Imaging Lecture Contents • Direct Imaging • Planet and Star Spatial Separation • Adaptive Optics • Direct Imaged Candidates • What is Being Measured? • Planet-Star Flux Ratios

  30. What is Being Measured?

  31. What is Being Measured? • Do we know the mass and radius of the planet? • Mass and radius are inferred from planet evolution models

  32. What is Being Measured? • Astronomers are measuring the planet flux at the detector • Flux = energy/(m2 s Hz)

  33. Flux from a Planet • Stars become fainter with increasing distance • Inverse square law • F ~ 1/D2 • Energy radiates outward • Think of concentric spheres centered on the star • The surface of each sphere has the same amount of energy per s passing through it • Energy = flux * surface area

  34. The History of Pluto’s Mass http://hoku.as.utexas.edu/~gebhardt/a309f06/plutomass.gif

  35. Planets • A flux measurement at visible wavelengths gives albedo*area • A flux measurement at thermal infrared wavelengths gives temperature*area • Same brightness from • A big, reflective and hence cold planet • A small, dark, and therefore hot planet • A combination gives of the two measurements gives: • Albedo, temperature, and area!

  36. Direct Imaging Lecture Contents • Direct Imaging • Planet and Star Spatial Separation • Adaptive Optics • Direct Imaged Candidates • What is Being Measured? • Planet-Star Flux Ratios

  37. In the interests of time I will skip the planet-star flux ratio derivation and leave it for you if you are interested

  38. Flux from a Planet • Stars become fainter with increasing distance • Inverse square law • F ~ 1/D2 • Energy radiates outward • Think of concentric spheres centered on the star • The surface of each sphere has the same amount of energy per s passing through it • Energy = flux * surface area • Flux at Earth

  39. Thermal Flux at Earth • Fp() is the flux at the planet surface • Fp () is the planet flux at Earth

  40. Visible-Wavelength Flux at Earth • Fp() is the flux at the planet surface • Fp () is the planet flux at Earth

  41. Planets at 10 pc Sun hot Jupiters J V E M Solar System at 10 pc (Seager 2003)

  42. Planet-Star Flux Ratio at Earth • Fp() is the flux at the planet surface • Fp () is the planet flux at Earth

  43. Thermal Emission Flux Ratio • Planet-to-star flux ratio • Black body flux • Take the ratio • Approximation for long wavelengths • Final flux ratio • Thermal emission is typically at infrared wavelengths

  44. Scattered-Light Flux Ratio • Planet-to-star flux ratio • Black body flux • Scattered stellar flux • Take the planet-to-star flux ratio • Scattered flux is usually at visible-wavelengths for planets

  45. Direct Imaging Lecture Summary • Direct Imaging • Diffraction limits detection • Spatial resolution • Diffracted light is brighter than planets • Direct Imaged Candidates • Four direct imaged planet candidates • Mass and radiusi are inferred from models • No way to confirm mass • What is Being Measured? • Flux at detector. • Other parameters are inferred • Planet-Star Flux Ratios • Approximations are useful for estimates

  46. Exoplanet Detection Techniques II • Planet Detection Techniques in More Detail • Direct Imaging • Microlensing • Astrometry

  47. Microlensing Lecture Contents • Gravitational Microlensing Overview • Planet-Finding Microlensing Concept • Tour of Planet Microlensing Light Curves

  48. Gravitational Lensing • Light from a very distant, bright source is "bent" around a massive object between the source object and the observer • A product of general relativity

  49. Gravitational Lensing • According to general relativity, mass "warps" space-time to create gravitational fields • When light travels through these fields it bends as a result • This theory was confirmed in 1919 during a solar eclipse when Arthur Eddington observed the light from stars passing close to the sun was slightly bent, so that stars appeared slightly out of position

  50. Strong Gravitational Lensing Image is distorted into a ring if the lens and source are perfecty aligned (and the lens is a “point” or spherical compact mass)

More Related