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1993-05-03
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASE Aug. 18, 1989
NASA's Voyager 2 spacecraft has detected intense
radio emissions from Neptune, indicating that the planet has
a magnetic field.
The discovery, made by Voyager 2's planetary radio
astronomy instrument team at NASA's Jet Propulsion
Laboratory, Pasadena, Calif., greatly increases the
likelihood that the spacecraft will discover a wide range of
interesting phenomena related to a magnetic field, such as
aurora and possible radiation-darkened ring arcs and moons
around Neptune.
Voyager 2 will come within 4,850 kilometers (3,000
miles) of Neptune at 9 p.m. on Aug. 24.
The emissions are generated around planets by
high-velocity, charged particles as they spiral along
magnetic field lines into the planet's atmosphere.
At Neptune, "the radio emissions are very intense,
very impulsive, and occur in a limited range of frequency,"
said Dr. James Warwick, principal investigator on the
planetary radio astronomy experiment. The emissions, he
added, are polarized, "so we know we're dealing with a
magnetic field. The source is not lightning; it is related
to energetic particles interacting in a magnetic field."
A planetary magnetic field is a girdle of magnetic
field lines that surround a planet. Such fields are thought
to be generated by fluid motion in a planet's core (molten
iron in Earth's core, for example). Mercury, Earth,
Jupiter, Saturn and Uranus have magnetic fields, while Venus
and Mars do not. Whether Pluto has one or not is not known.
While the Neptunian radio emissions were only
confirmed today, Warwick said that in looking back over
Voyager data, the emissions were heard by the planetary
radio astronomy instrument as early as Aug. 14. The
emissions weren't immediately recognized as being associated
with Neptune, however, because their character "was so
different from what we were expecting," Warwick said.
As more data from the instrument is returned to
Earth over coming days, Warwick's team will be able to
precisely define Neptune's rotation -- the length of its day.
Early analysis indicates that Neptune's magnetic
field is of an intensity similar to the magnetic fields of
Earth and Uranus.
Voyager 2's close flyby over Neptune's northern
hemisphere will allow the spacecraft's complement of
instruments to determine Neptune's magnetic field structure
and orientation.
The Voyager Mission is conducted for NASA's Office
of Space Science by the Jet Propulsion Laboratory.
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#1261mbm
8/18/89