Glory revealed in disk-integrated photometry of Venus

被引:28
作者
Garcia Munoz, A. [1 ]
Perez-Hoyos, S. [2 ,3 ]
Sanchez-Lavega, A. [2 ,3 ]
机构
[1] Estec, ESA RSSD, NL-2201 AZ Noordwijk, Netherlands
[2] Univ Basque Country, Grp Ciencias Planetarias, Dept Fis Aplicada 1, ETS Ingn, Bilbao 48013, Spain
[3] UPV EHU IAA CSIC, Unidad Asociada Grp Ciencias Planetarias, Bilbao 48008, Spain
关键词
techniques: photometric; planets and satellites: atmospheres; radiative transfer; PLANETARY-ATMOSPHERES; EXTRASOLAR PLANETS; CLOUD MICROPHYSICS; LIGHT-SCATTERING; PHASE FUNCTION; EARTH; WATER; POLARIZATION; JUPITER; MERCURY;
D O I
10.1051/0004-6361/201423531
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Context. Reflected light from a spatially unresolved planet yields unique insight into the overall optical properties of the planet cover. Glories are optical phenomena caused by light that is backscattered within spherical droplets following a narrow distribution of sizes; they are well known on Earth as localised features above liquid clouds. Aims. Here we report the first evidence for a glory in the disk-integrated photometry of Venus and, in turn, of any planet. Methods. We used previously published phase curves of the planet that were reproduced over the full range of phase angles with model predictions based on a realistic description of the Venus atmosphere. We assumed that the optical properties of the planet as a whole can be described by a uniform and stable cloud cover, an assumption that agrees well with observational evidence. Results. We specifically show that the measured phase curves mimic the scattering properties of the Venus upper-cloud micron-sized aerosols, also at the small phase angles at which the glory occurs, and that the glory contrast is consistent with what is expected after multiple scattering of photons. In the optical, the planet appears to be brighter at phase angles of similar to 11-13 degrees than at full illumination; it undergoes a maximum dimming of up to similar to 10% at phases in between. Conclusions. Glories might potentially indicate spherical droplets and, thus, extant liquid clouds in the atmospheres of exoplanets. A prospective detection will require exquisite photometry at the small planet-star separations of the glory phase angles.
引用
收藏
页数:6
相关论文
共 60 条
[1]   The mathematical physics of rainbows and glories [J].
Adam, JA .
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 2002, 356 (4-5) :229-365
[3]  
ARKING A, 1968, J ATMOS SCI, V25, P617, DOI 10.1175/1520-0469(1968)025<0617:TPCOVA>2.0.CO
[4]  
2
[5]   Rainbows, polarization, and the search for habitable planets [J].
Bailey, Jeremy .
ASTROBIOLOGY, 2007, 7 (02) :320-332
[6]   EXOPLANET ALBEDO SPECTRA AND COLORS AS A FUNCTION OF PLANET PHASE, SEPARATION, AND METALLICITY [J].
Cahoy, Kerri L. ;
Marley, Mark S. ;
Fortney, Jonathan J. .
ASTROPHYSICAL JOURNAL, 2010, 724 (01) :189-214
[7]  
CARLSON BE, 1988, J ATMOS SCI, V45, P2066, DOI 10.1175/1520-0469(1988)045<2066:CMOTGP>2.0.CO
[8]  
2
[9]   Detection of Earth-like planets around nearby stars using a petal-shaped occulter [J].
Cash, W .
NATURE, 2006, 442 (7098) :51-53
[10]   POLARIZATION AND SCATTERING CHARACTERISTICS IN THE ATMOSPHERES OF EARTH, VENUS, AND JUPITER [J].
COFFEEN, DL .
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA, 1979, 69 (08) :1051-&