Ge_2019_AJ_157_89.pdf (9.15 MB)
Rotational Light Curves of Jupiter from Ultraviolet to Mid-infrared and Implications for Brown Dwarfs and Exoplanets
journal contributionposted on 2019-06-25, 14:46 authored by H Ge, X Zhang, LN Fletcher, GS Orton, J Sinclair, J Fernandes, T Momary, Y Kasaba, TM Sato, T Fujiyoshi
Rotational modulations are observed on brown dwarfs and directly imaged exoplanets, but the underlying mechanism is not well understood. Here we analyze Jupiter’s rotational light curves at 12 wavelengths from the ultraviolet (UV) to the mid-infrared (mid-IR). The peak-to-peak amplitudes of Jupiter’s light curves range from subpercent to 4% at most wavelengths, but the amplitude exceeds 20% at 5 μm, a wavelength sensing Jupiter’s deep troposphere. Jupiter’s rotational modulations are primarily caused by discrete patterns in the cloudless belts instead of the cloudy zones. The light-curve amplitude is controlled by the sizes and brightness contrasts of the Great Red Spot (GRS), expansions of the North Equatorial Belt (NEB), patchy clouds in the North Temperate Belt (NTB), and a train of hot spots in the NEB. In reflection, the contrast is controlled by upper tropospheric and stratospheric hazes, clouds, and chromophores in the clouds. In thermal emission, the small rotational variability is caused by the spatial distribution of temperature and opacities of gas and aerosols; the large variation is caused by the NH3 cloud holes and thin-thick clouds. The methane-band light curves exhibit opposite-shape behavior compared with the UV and visible wavelengths, caused by a wavelength-dependent brightness change of the GRS. Light-curve evolution is induced by periodic events in the belts and longitudinal drifting of the GRS and patchy clouds in the NTB. This study suggests several interesting mechanisms related to distributions of temperature, gas, hazes, and clouds for understanding the observed rotational modulations on brown dwarfs and exoplanets.
This research was supported by a NASA Earth and Space Science Fellowship to H.G., and NASA Solar System Workings grant NNX16AG08G and the Hellman Fellowship to X.Z. This research also benefited from the Outer Planetary Atmosphere Legacy project at https://archive.stsci.edu/prepds/opal/. L.N.F. was supported by a Royal Society Research Fellowship and European Research Council Consolidator Grant (under the European Union's Horizon 2020 research and innovation program, grant agreement No. 723890) at the University of Leicester. G.S.O. and J.F. were supported by funds from NASA, distributed to the Jet Propulsion Laboratory, California Institute of Technology; J.F. was supported through JPL's Year-round Internship Program (YIP). This investigation was partially based on thermal-infrared observations acquired at (i) the ESO Very Large Telescope Paranal UT3/Melipal Observatory (program ID 096.C-0091); (ii) the Subaru Telescope and obtained from the SMOKA database, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan (program ID S16B-049); and (iii) NASA's Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration (program ID 2016A-022).
CitationAstronomical Journal, 2019, 157 (2)
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy
- VoR (Version of Record)