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uranusb.txt
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1996-01-12
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PHOTO RELEASE NO.: STScI-PRC94-50b RELEASE DATE: November 2, 1994
HUBBLE OBSERVES THE PLANET URANUS
This NASA Hubble Space Telescope image of the planet Uranus reveals
the planet's rings and bright clouds and a high altitude haze above the
planet's south pole.
Hubble's new view was obtained on August 14, 1994, when Uranus was
1.7 billion miles (2.8 billion kilometers) from Earth. These details, as
imaged by the Wide Field Planetary Camera 2, were only previously seen
by the Voyager 2 spacecraft, which flew by Uranus in 1986. Since then,
none of these inner satellites has been further observed, and detailed
observations of the rings have not been possible.
Though Uranus' rings were discovered indirectly in 1977 (through stellar
occultation observations), they have never before been seen in visible light
through a ground-based telescope.
Hubble resolves several of Uranus' rings, including the outermost Epsilon
ring. The planet has a total of 11 concentric rings of dark dust. Uranus is
tipped such that its rotation axis lies in the plane of its orbit, so the rings
appear nearly face-on.
Three of Uranus' inner moons each appear as a string of three dots at the
bottom of the picture. This is because the picture is a composite of three
images, taken about six minutes apart, and then combined to show the
moons' orbital motions. The satellites are, from left to right, Cressida,
Juliet, and Portia. The moons move much more rapidly than our own
Moon does as it moves around the Earth, so they noticeably change
position over only a few minutes.
One of the four gas giant planets of our solar system, Uranus is largely
featureless. HST does resolve a high altitude haze which appears as a
bright "cap" above the planet's south pole, along with clouds at southern
latitudes (similar structures were observed by Voyager). Unlike Earth,
Uranus' south pole points toward the Sun during part of the planet's 84-year
orbit. Thanks to its high resolution and ability to make observations over
many years, Hubble can follow seasonal changes in Uranus's atmosphere,
which should be unusual given the planet's large tilt.
Credit: Kenneth Seidelmann, U.S. Naval Observatory,
and NASA
These observations were conducted by a team led by Dr. Ken Seidelmann
of the U.S. Naval Observatory as Principal Investigator. These images
have been processed by Professor Douglas Currie and Mr. Dan Dowling in
the Department of Physics at the University of Maryland. Other team
members are Dr. Ben Zellner at Georgia Southern University, Dr. Dan
Pascu and Mr. Jim Rhode at the U.S. Naval Observatory, and Dr. Ed
Wells, Mr. Charles Kowal (Computer Science Corporation) and Dr. Alex
Storrs of the Space Telescope Science Institute.