The ansae of the Io plasma torus, with Jupiter.
[Click on the picture for a larger version.] These images, taken at the McMath-Pierce solar
telescope at Kitt Peak,
are from an ongoing imaging program: a custom-built instrument simultaneously
images both ansae (sides) of the torus in singly ionized sulfur, together an
image of Jupiter for improved spatial and intensity calibration. You can read
more about this program in my 1999
AAS, 2000 AGU, and 2000 DPS meeting presentations.
Hydrogen and oxygen emission near Io. This is a composite of two
pictures of Io acquired in the far ultraviolet with the
Telescope Imaging Spectrograph: netural oxygen is shown in red and
hydrogen in green. (The blue circle marks Io's limb.) The oxygen emission (and
some similar-looking neutral sulfur emission) comes from neutral gas near Io,
whereas most of the hydrogen emission appears to be reflected sunlight. For
more info, check out my article in Science.
[S II] 6731Å emission from
the east ansa of the Io plamsa torus on December 3, 1988, at 6:36
UT (from my dissertation).
The part inside the blue circle is the actual image I got through the
telescope (the McMath-Pierce solar
telescope at Kitt
Peak), consisting of light given off by ionized sulfur; the
positions of Jupiter (red circle), Io (yellow dot), and Io's orbit
(yellow ellipse) were calculated and added into
the image later. The plasma, being electrically charged, is bound to
Jupiter's magnetic field, which, like the Earth's, is not quite
aligned with its spin; this is why the torus does not "line
up" with Io's orbit. A version of this image is available for use as wallpaper here.