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juparcs.txt
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1994-10-05
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PHOTO RELEASE NO.: STScI-PRC94-45 FOR RELEASE: September 29,1994
HUBBLE SEES AURORAL EMISSION ARCS FOLLOWING THE K IMPACT
This far-ultraviolet image of Jupiter taken with NASA's Hubble
Space Telescope (HST) shows narrow auroral "arcs" that appeared
at northern mid-latitudes following the impact of the K nucleus
fragment of comet P/Shoemaker-Levy 9. (The dark K impact region
is on the left limb, followed, from left to right, by the C, A,
and E comet impact regions.)
The image was taken on 19 July 1994, 45 minutes after the K
nucleus slammed into the gas giant planet. The image shows
arc-like auroral emissions near the western (left) limb at
mid-latitudes in the north, and fainter but remarkably similar
emissions near the K impact site in the south.
The "arcs" are being produced by energetic charged particles,
like the other auroral emissions, except that they appear to last
less than one hour and they are at a location where Jupiter
normally does not have aurora. They were apparently produced by
the K impact, even though they appear bright in the northern
hemisphere nearly 70,000 miles away from the impact site.
The overlay of magnetic field lines shows the path of the charged
particles near Jupiter (from a model based on Pioneer and Voyager
spacecraft data), starting at the northern "arcs" and tracing the
magnetic field back to the impact site in the southern
atmosphere. (There is an overlay of a longitude/latitude grid to
indicate locations on Jupiter).
Aurorae, also known as the northern and southern lights, are
produced by high energy charged particles, trapped in Jupiter's
magnetic field, that cause atmosphereic gasses to glow.
Based on comparison with ROSAT satellite X-ray images of Jupiter
also taken at time of the K impact, astronomers know that the
northern disturbance was brightest near the time of the K impact,
and then faded. If HST images had been taken during the K
impact, they would likely have shown far brighter arcs than those
observed 45 min. later.
The image was taken with the Wide Field Planetary Camera-2 at UV
wavelengths (1300-2100 Angstroms), where the polar regions
normally appear dark and the northern and southern lights are
clearly visible.
Credit: John T. Clarke (U. of Michigan),
and NASA