skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Near-infrared brightness of the Galilean satellites eclipsed in Jovian shadow: A new technique to investigate Jovian upper atmosphere

Abstract

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{sup –6}-10{sup –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 ismore » important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.« less

Authors:
 [1]; ; ; ;  [2];  [3]; ;  [4];  [5];  [6]; ;  [7];  [8];  [9];  [10]
  1. Frontier Research Institute for Interdisciplinary Science, Tohoku University, Sendai, Miyagi 980-8578 (Japan)
  2. Department of Space Astronomy and Astrophysics, Institute of Space and Astronoutical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-5210 (Japan)
  3. Department of Astronomy, Arizona University, Tucson, AZ 85721 (United States)
  4. Hawaii Observatory, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States)
  5. Research Center for Advanced Information Science and Technology, Aizu Research Cluster for Space Science, The University of Aizu, Aizu-Wakamatsu, Fukushima 965-8589 (Japan)
  6. Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550 (Japan)
  7. Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan)
  8. Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581 (Japan)
  9. Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8551 (Japan)
  10. Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22365700
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 789; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATMOSPHERES; BRIGHTNESS; ECLIPSE; FREQUENCY DEPENDENCE; LUMINOSITY; NEAR INFRARED RADIATION; SATELLITES; SPACE; SPECTRA; SPECTROSCOPY; TELESCOPES; TRANSMISSION; VISIBLE RADIATION

Citation Formats

Tsumura, K., Arimatsu, K., Matsuura, S., Shirahata, M., Wada, T., Egami, E., Hayano, Y., Minowa, Y., Honda, C., Kimura, J., Kuramoto, K., Takahashi, Y., Nakajima, K., Nakamoto, T., and Surace, J., E-mail: tsumura@astr.tohoku.ac.jp. Near-infrared brightness of the Galilean satellites eclipsed in Jovian shadow: A new technique to investigate Jovian upper atmosphere. United States: N. p., 2014. Web. doi:10.1088/0004-637X/789/2/122.
Tsumura, K., Arimatsu, K., Matsuura, S., Shirahata, M., Wada, T., Egami, E., Hayano, Y., Minowa, Y., Honda, C., Kimura, J., Kuramoto, K., Takahashi, Y., Nakajima, K., Nakamoto, T., & Surace, J., E-mail: tsumura@astr.tohoku.ac.jp. Near-infrared brightness of the Galilean satellites eclipsed in Jovian shadow: A new technique to investigate Jovian upper atmosphere. United States. doi:10.1088/0004-637X/789/2/122.
Tsumura, K., Arimatsu, K., Matsuura, S., Shirahata, M., Wada, T., Egami, E., Hayano, Y., Minowa, Y., Honda, C., Kimura, J., Kuramoto, K., Takahashi, Y., Nakajima, K., Nakamoto, T., and Surace, J., E-mail: tsumura@astr.tohoku.ac.jp. Thu . "Near-infrared brightness of the Galilean satellites eclipsed in Jovian shadow: A new technique to investigate Jovian upper atmosphere". United States. doi:10.1088/0004-637X/789/2/122.
@article{osti_22365700,
title = {Near-infrared brightness of the Galilean satellites eclipsed in Jovian shadow: A new technique to investigate Jovian upper atmosphere},
author = {Tsumura, K. and Arimatsu, K. and Matsuura, S. and Shirahata, M. and Wada, T. and Egami, E. and Hayano, Y. and Minowa, Y. and Honda, C. and Kimura, J. and Kuramoto, K. and Takahashi, Y. and Nakajima, K. and Nakamoto, T. and Surace, J., E-mail: tsumura@astr.tohoku.ac.jp},
abstractNote = {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{sup –6}-10{sup –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.},
doi = {10.1088/0004-637X/789/2/122},
journal = {Astrophysical Journal},
number = 2,
volume = 789,
place = {United States},
year = {Thu Jul 10 00:00:00 EDT 2014},
month = {Thu Jul 10 00:00:00 EDT 2014}
}
  • The present near-IR (2.2-, 3.8-, 4.8-micron) lightcurves and phase coefficients for the Galilean satellites notes the geometric albedo of Io to include volcanic emission at the two longer wavelengths, although no major outbursts were detected during the 1982-1983 period of these observations. The trend of decreasing albedo with increasing wavelength exhibited by Ganymede and Europa is consistent with their possession of icy surfaces. The results obtained for Callisto are consistent with visible-wavelength observations of other dark solar system objects. 35 references.
  • Heavy ions produced in the atmosphere of the Galilean satellites are a potentially significant source of plasma in the Jovian magnetosphere. Such ions will rapidly be accelerated to the corotation velocity, and the associated centrifugal force far exceeds that of gravity. Satellite ions are thus confined near the equator with a centrifugal scale height that depends linearly on their thermal velocity (unlike the ordinary gravitational scale height, which depends linearly on the temperature). We find that this centrifugal scale height is independent of the distance from Jupiter. The satellite ions, as they diffuse radially through the magnetosphere, will form amore » current sheet of roughly uniform thickness of the order of 1 R/sub J/ (Jupiter radius). This current sheet produces a sharp cusplike distortion of the magnetic field, in contrast to the large-scale distortion that is produced by ions from Jupiter's atmosphere, which are less equatorially confined. This current sheet may significantly affect the field geometry near the equatorial plane, but the total outward distortion caused by satellite ions would be comparable to that produced by Jovian atmospheric ions only if all the Galilean satellites were to produce heavy ions with a source flux comparable to the photo-ion flux from the Jovian atmosphere. (AIP)« less
  • From results of ionospheric investigations made by the Cosmos 3 and Cosmos 5 satellites, some deductions were made on atmospheric density, based on observed decelerations of the satellites as they passed through their perigees. Variations in orbital period and in perigee altitude are presented as a function of several months of orbiting time and are plotted for comparison against satellite latitude and local time. The resulting graph for Cosmos 5 for the period June to November 1962 shows that the perigee fluctuated periodically between extremes of about 190 and 208 km. These periodic fluctuations are ascribed mainly to the nonsphericitymore » of the earth and to the fact that the center of gravitational attraction is not coincident with the earth's center. Also, orbit time was shortest and perigee altitude highest when the perigee occurred at high southern (winter) latitudes and on the earth's night side, i.e., during the coldest ionospheric conditions. Analogous results were found for Cosmos 3 for the April to May interval. Expressions were developed that relate the rate of retardation to atmospheric density in the vicinity of the perigee. From the retardation data of the two satellites it was thus possible to estimate a range of densities in the region of 200 to 230 km; this was done after assuming values of 30 to 80 km for the height of the nominally uniform troposphere. mits of density so derived were 5.8 to 4.1 x 10/sup -13/ g/cm/sup 3/ at 200 km and 3.7 to 2.6 x 10/sup -13/ g/cm/sup 3/ at 230 km. (AID)« less