1. Spectroscopic Observations of HD 209458 b Lewis Kotredes Ge/Ay 132 Final

2. Background According to http://exoplanets.org, there are 110 currently known extrasolar planets According to http://exoplanets.org, there are 110 currently known extrasolar planetshttp://exoplanets.org Most extrasolar planets were detected using high-precision radial velocity surveys Most extrasolar planets were detected using high-precision radial velocity surveys Several of these planets are known to undergo transits; partial occultations of their host stars by the planets Several of these planets are known to undergo transits; partial occultations of their host stars by the planets HD 209458 b is the most studied of these HD 209458 b is the most studied of these

3. HD 209458 b HD 209458 is a star of spectral class G0V, with a V magnitude of 7.65 HD 209458 is a star of spectral class G0V, with a V magnitude of 7.65 This star has one known planet with a period of 3.525 days This star has one known planet with a period of 3.525 days In 2000 it was announced that this planet undergoes transits with a depth of ~1.5% In 2000 it was announced that this planet undergoes transits with a depth of ~1.5%

4. Transmission Spectroscopy Direct spectroscopy of the planets so far discovered is difficult due to the high contrast ratio between close companions Direct spectroscopy of the planets so far discovered is difficult due to the high contrast ratio between close companions For transiting planets, atmospheres can be probed by examining their effects on starlight For transiting planets, atmospheres can be probed by examining their effects on starlight

5. Transmission Spectroscopy Using narrow-band filters specific spectral lines in the atmosphere can be observed as changes to measured transit depth Using narrow-band filters specific spectral lines in the atmosphere can be observed as changes to measured transit depth Spectra of the star in and out of transit can be compared to see spectral features Spectra of the star in and out of transit can be compared to see spectral features Secondary eclipses can be examined for reflected planetary spectra Secondary eclipses can be examined for reflected planetary spectra

6. Na The first detection of a species in an exoplanet atmosphere was accomplished using narrow-band filters The first detection of a species in an exoplanet atmosphere was accomplished using narrow-band filters Charbonneau et al used a filter designed to observe the Na D lines on STIS and measured a 3  change to transit depth Charbonneau et al used a filter designed to observe the Na D lines on STIS and measured a 3  change to transit depth

7. Ly  Vidal-Madjar et al used a grating spectrometer with STIS to examine the transit of HD 209458 b Vidal-Madjar et al used a grating spectrometer with STIS to examine the transit of HD 209458 b The measured depth of the transit in this line was 15%, much higher than the measured optical depth The measured depth of the transit in this line was 15%, much higher than the measured optical depth This suggests an atmospheric radius larger than the Roche limit This suggests an atmospheric radius larger than the Roche limit

8. OI and CII Further measurements by Vidal-Madjar et al suggest the presence of OI and CII in the extended outer atmosphere Further measurements by Vidal-Madjar et al suggest the presence of OI and CII in the extended outer atmosphere The transit depth for these species is greater than that of Na, but not so great as for HI The transit depth for these species is greater than that of Na, but not so great as for HI

9. Infrared Spectra Many attempts have been made to detect CO lines (around 2.2  m) in the atmosphere of HD 209458 b Many attempts have been made to detect CO lines (around 2.2  m) in the atmosphere of HD 209458 b Some of these attempts have used “occultation spectroscopy” of the secondary eclipse, and have produced upper limits on this species Some of these attempts have used “occultation spectroscopy” of the secondary eclipse, and have produced upper limits on this species

10. Conclusions Attempts to measure spectra of extrasolar planets are still in the nascent stages Attempts to measure spectra of extrasolar planets are still in the nascent stages As more transiting planets are discovered, we are developing tools to learn about them As more transiting planets are discovered, we are developing tools to learn about them