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The Devil’s in the Details

The Devil’s in the Details. Transits in detail Telescopes. Last time…. Radial velocity Measures Doppler shift Planet’s mass Must be in line-of-sight of observer Need a large telescope for high-precision measurements 1 m/s ~ 1 Earth-sized planet, need 6 m class telescope Transit

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The Devil’s in the Details

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  1. The Devil’s in the Details Transits in detailTelescopes

  2. Last time…. • Radial velocity • Measures Doppler shift • Planet’s mass • Must be in line-of-sight of observer • Need a large telescope for high-precision measurements • 1 m/s ~ 1 Earth-sized planet, need 6 m class telescope • Transit • Measures drop in light as planet moves in front of or behind host star • Planet’s radius • Must be in line-of-sight of observer • Can do with a relatively small telescope

  3. Transit • What is it measuring?

  4. Transit • The atmosphere + the planet’s disk

  5. Transit • The atmosphere + the planet’s optically-thick disk

  6. Transit • The atmosphere + the planet’s optically-thick disk

  7. Transit • Amount of atmospheric absorption will change with wavelength

  8. Transit • Amount of atmospheric absorption will change with wavelength

  9. Transit • So a planet’s radius will change with wavelength due to absorption by different molecules in its atmosphere

  10. So…. • If we measure the transit of an exoplanet at different wavelengths… • We can measure how its radius varies with wavelength • Indicates its atmospheric structure and content • Atmospheric structure = how temperature varies with altitude • Atmospheric content = what molecules are present

  11. Example! • Detection of H2 scattering Zellem et al. (in prep.)

  12. Example! • Detection of H2 scattering

  13. Another Example! • Detection of water, methane, and carbon dioxide in a hot Jupiter’s atmosphere Swain et al. (2009)

  14. Measuring radii at the 61” • Planet has same signature in the infrared (IR) despite differing atmospheric contents • Signal very different in the optical Benneke & Seager (2013)

  15. Why are the IR signatures the same? • In the IR, a small planet with a thick atmosphere can block as much light as a large planet with a small atmosphere • Hot Jupiter atmospheres are opaque in the IR

  16. Why are the IR signatures the same? • In the IR, a small planet with a thick atmosphere can block as much light as a large planet with a small atmosphere • Hot Jupiter atmospheres are opaque in the IR =

  17. However, not the same in the visible • In the visible, the planet’s atmosphere is now transparent, so a small planet will look different than a large one

  18. However, not the same in the visible • In the visible, the planet’s atmosphere is now transparent, so a small planet will look different than a large one ≠

  19. Rob does spectroscopy magic

  20. Measuring radii at the 61” • Planet has same signature in the infrared (IR) despite differing atmospheric contents • Signal very different in the optical Benneke & Seager (2013)

  21. Telescopes

  22. History • First telescopes were refractors in the Netherlands in 1608 • Galileo heard about them in 1609 and built his own • First person to point towards the heavens • Discovered craters on Moon, moons of Jupiter, Saturn’s rings

  23. Refractors vs. Reflectors • Refractor: objective lens on front refracts (focuses) light at the back end of the telescope • Lens can obscure image • Very long focal length, so telescope itself is long

  24. Refractors vs. Reflectors • Reflector: primary mirror reflects light to a focal point • No more lens • Can reflect the image back on itself, makes shorter focal length and telescope • Developed by Newton in 1680 • Most professional telescopes today are reflectors Schmidt-Cassegrain design

  25. What is the 61”? • Reflector or refractor?

  26. What is the 61”? • Light comes in the dome, hits primary mirror

  27. What is the 61”? • Reflected off of primary mirror and focused on secondary mirror

  28. What is the 61”? • Light reflects off of secondary mirror and is focused on detector

  29. What is the 61”? • REFLECTOR

  30. Next time…. • Learn about instrumentation used to collect data • CCDs • Spectrographs • Start learning how we will reduce telescopic data

  31. Calendar • Next class: Friday October 24 • Field trips! • Visit the 61” on Mount Bigelow • Afternoon of Saturday November 1 • Limited space for those who want to stick around through the night to help observe • Will need people willing to help drive/carpool up the mountain • Mirror Lab Tour • Friday November 14 from 4-5 PM

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