TOPS Io Volcano Observations
On June 22 1999, during the 1999 TOPS student/teacher astronomy workshop in Waimea, Hawaii,
I demonstrated some "live" astronomy by conducting a remote observing run
on the NASA Infrared Telescope Facility
(IRTF) from the Keck headquarters building in Waimea. The run was part of
my long-term program to monitor volcanic
activity on Jupiter's moon Io by observing the near-infrared volcanic radiation
from the moon.
Pictures of the observing session
Taken by Karen Meech. Click on thumbnail for full-sized image.
We were very lucky to observe an unusually bright volcanic eruption on Io during
the TOPS demonstration. I discovered the eruption during the first part of
the observing run, which involved observing Io's passage into Jupiter's shadow
(an eclipse) and then its disappearance behind Jupiter itself (an occultation).
I made these observations at the IRTF, on the summit of Mauna Kea.
While Io completed its two-hour passage behind Jupiter I drove from the summit
down to Waimea so I could observe Io's reappearance from behind Jupiter
with the TOPS participants.
[Stuff on the techniques used to be inserted here]
Results from the Observations
- This was the fourth-brightest eruption that we have observed in our
program of over 200 nights at the telescope, perhaps the tenth-brightest
ever seen on Io, and the brightest for which we have obtained such high-quality
observations. At some wavelengths, it is several times brighter than the brightest
eruption observed on Io by the Galileo spacecraft. We have given the
eruption the romantic name of 9906A.
- By timing the disappearance and reappearance of the volcano behind Jupiter,
we now have a fairly good idea of its location, which is at 20 W, 25 S, probably
at a volcano named Catequil Patera.
- A quick look at the data indicates that the amount of hot material exposed
during the eruption was equivalent to a 2.5 mile diameter region at 1900 degrees
Farenheit. This is a far bigger area of hot material than is exposed during
the eruptions of Kilauea, for example.
- Observations by Bob Howell at the Wyoming Infrared Observatory saw the
same eruption again a week later. It had faded several-fold but was still
the brightest eruption visible on Io. At the same time, the
took its closest-yet images of Io, which included a look at the location
of the eruption. Galileo saw the eruption as a very bright glow in images
taken, like many of our IRTF images, when Io was in Jupiter's shadow.
We are still waiting to see if there
is debris from the eruption blanketing the surrounding terrain,
or a plume of material being blasted into space from the volcano. Both
plume and a
debris blanket were seen during a similar or smaller eruption at the Io volcano Pillan
that was observed by the Galileo spacecraft in 1997.
Sequence of images of Io volcano 9906A disappearing behind Jupiter.
Sequence lasts 35 seconds, wavelength is 3.5 microns. The exact time of
disappearance gives the location of the volcano on Io.
Click on the thumbnail
for a full-sized version.
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