The Very Low Albedo of an Extrasolar Planet: MOST Space-based Photometry of HD 209458

By J. Rowe, J. Matthews, Sara Seager, E. Miller-Ricci, D. Sasselov, R. Kuschnig, D. Guenther, A. Moffat, S. Rucinski, G. Walker and 1 more. 2007

182 citations recorded by the source corpus.

Measuring the albedo of an extrasolar planet provides insight into its atmospheric composition and its global thermal properties, including heat dissipation and weather patterns. Such a measurement requires very precise photometry of a transiting system, fully sampling many phases of the secondary eclipse. Space-based optical photometry of the transiting system HD 209458 from the MOST (Microvariablity and Oscillations of Stars) satellite, spanning 14 and 44 days in 2004 and 2005, respectively, allows us to set a sensitive limit on the optical eclipse of the hot exosolar giant planet in this system. Our best fit to the observations yields a flux ratio of the planet and star of 7 ± 9 ppm (parts per million), which corresponds to a geometric albedo through the MOST bandpass (400-700 nm) of Ag = 0.038 ± 0.045. This gives a 1 σ upper limit of 0.08 for the geometric albedo and a 3 σ upper limit of 0.17. HD 209458b is significantly less reflective than Jupiter (for which Ag would be about 0.5). This low geometric albedo rules out the presence of bright reflective clouds in this exoplanet’s atmosphere. We determine refined parameters for the star and exoplanet in the HD 209458 system based on a model fit to the MOST light curve.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6f1cfb469bd6eb1f520a42144cf3407fb220303c

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In Astronomy and Astrophysics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. M. Line
5. J. D'esert
6. Sara Seager
7. Laura Kreidberg
8. D. Deming

In Instrumentation

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. M. Line
5. J. D'esert
6. Laura Kreidberg
7. J. Southworth
8. Sara Seager

Citations in the corpus

• THE STATISTICS OF ALBEDO AND HEAT RECIRCULATION ON HOT EXOPLANETS (2009, methodology): “It is telling that the only optical measurement in Table 1 that is unanimously considered to constrain albedo — and not thermal emission— is the MOST observations of HD 209458b (Rowe et al. 2008), the coolest of the five transiting planets with optical photometric constraints.”
• A TEMPERATURE AND ABUNDANCE RETRIEVAL METHOD FOR EXOPLANET ATMOSPHERES (2009, methodology): “Even if one were to assume AB = 0.3 (a relatively high value for hot Jupiters; see Rowe et al. 2008), fr can be as high as 0.46, indicating very efficient redistribution.”
• WASP-19b: THE SHORTEST PERIOD TRANSITING EXOPLANET YET DISCOVERED (2010, background): “Many, but not all, “hot Jupiters” have temperature inversions in their atmospheres (e.g., Knutson et al. 2008), and they can have very low optical albedos (Rowe et al. 2008).”
• NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST/WFC3 SPECTROSCOPY (2016, background): “The very low geometric albedo from MOST for this planet (Rowe et al. 2008) suggests a low Bond albedo, which favors the explanation that energy is being advected to the night side, as seen in the 4.5 µm light curve from Zellem et al. (2014).”
• A chemical model for the atmosphere of hot Jupiters (2012, background): “The physical properties of HD 209458b have been refined by Rowe et al. (2008) and are presented in Table 1, with some properties of the host star.”
• Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in (2008, background): “They are supported by the upper limit for the albedo of HD 209458b recently derived by Rowe et al. (2006, 2008).”