 Satellite
Footprints Seen in Jupiter Aurora
This is a spectacular NASA Hubble Space Telescope
close-up view of an electric-blue aurora that is eerily glowing
one half billion miles away on the giant planet Jupiter. Auroras
are curtains of light resulting from high-energy electrons racing
along the planet's magnetic field into the upper atmosphere. The
electrons excite atmospheric gases, causing them to glow. The image
shows the main oval of the aurora, which is centered on the magnetic
north pole, plus more diffuse emissions inside the polar cap.
Though the aurora resembles the same phenomenon that
crowns Earth's polar regions, the Hubble image shows unique emissions
from the magnetic "footprints" of three of Jupiter's largest moons.
(These points are reached by following Jupiter's magnetic field
from each satellite down to the planet).
Auroral footprints can be seen in this image from
Io (along the left hand limb), Ganymede (near the center), and Europa
(just below and to the right of Ganymede's auroral footprint). These
emissions, produced by electric currents generated by the satellites,
flow along Jupiter's magnetic field, bouncing in and out of the
upper atmosphere. They are unlike anything seen on Earth.
This ultraviolet image of Jupiter was taken with the
Hubble Space Telescope Imaging Spectrograph (STIS) on November 26,
1998. In this ultraviolet view, the aurora stands out clearly, but
Jupiter's cloud structure is masked by haze.
December 14, 2000 inaugurates an intensive two weeks
of joint observation of Jupiter's aurora by Hubble and the Cassini
spacecraft. Cassini will make its closest approach to Jupiter enroute
to a July 2004 rendezvous with Saturn. A second campaign in January
2001 will consist of Hubble images of Jupiter's day-side aurora
and Cassini images of Jupiter’s night-side aurora, obtained just
after Cassini has flown past Jupiter. The team will develop computer
models that predict how the aurora operates, and this will yield
new insights into the effects of the solar wind on the magnetic
fields of planets.
Credit: NASA/ESA,
John Clarke (University of Michigan)
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STScI-PRC00-38
The
Space Telescope Science Institute
is operated by the Association
of Universities for Research in Astronomy, Inc. (AURA), for NASA,
under contract with the Goddard
Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project
of international cooperation between NASA and the
European Space Agency (ESA).
