TY - JOUR
T1 - Near-infrared brightness of the Galilean satellites eclipsed in Jovian shadow
T2 - A New Technique to Investigate Jovian Upper Atmosphere
AU - Tsumura, K.
AU - Arimatsu, K.
AU - Egami, E.
AU - Hayano, Y.
AU - Honda, C.
AU - Kimura, J.
AU - Kuramoto, K.
AU - Matsuura, S.
AU - Minowa, Y.
AU - Nakajima, K.
AU - Nakamoto, T.
AU - Shirahata, M.
AU - Surace, J.
AU - Takahashi, Y.
AU - Wada, T.
PY - 2014/7/10
Y1 - 2014/7/10
N2 - Based on observations from the Hubble Space Telescope and the Subaru Telescope, we have discovered that Europa, Ganymede, and Callisto are bright around 1.5 μm even when not directly lit by sunlight. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was 10-6-10-7 of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at 1.5 μm, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 μm by the Spitzer Space Telescope, but it was not detected, suggesting a significant wavelength dependence. It is still unknown why they are luminous even when in the Jovian shadow, but forward-scattered sunlight by hazes in the Jovian upper atmosphere is proposed as the most plausible candidate. If this is the case, observations of these Galilean satellites while eclipsed by the Jovian shadow provide us with a new technique to investigate the Jovian atmospheric composition. Investigating the transmission spectrum of Jupiter by this method is important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.
AB - Based on observations from the Hubble Space Telescope and the Subaru Telescope, we have discovered that Europa, Ganymede, and Callisto are bright around 1.5 μm even when not directly lit by sunlight. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was 10-6-10-7 of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at 1.5 μm, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 μm by the Spitzer Space Telescope, but it was not detected, suggesting a significant wavelength dependence. It is still unknown why they are luminous even when in the Jovian shadow, but forward-scattered sunlight by hazes in the Jovian upper atmosphere is proposed as the most plausible candidate. If this is the case, observations of these Galilean satellites while eclipsed by the Jovian shadow provide us with a new technique to investigate the Jovian atmospheric composition. Investigating the transmission spectrum of Jupiter by this method is important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.
KW - atmospheric effects - eclipses planets and satellites
KW - individual (Jupiter, Europa, Ganymede, Callisto)
UR - http://www.scopus.com/inward/record.url?scp=84903273511&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84903273511&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/789/2/122
DO - 10.1088/0004-637X/789/2/122
M3 - Article
AN - SCOPUS:84903273511
SN - 0004-637X
VL - 789
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 122
ER -