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Calar Alto Images of Fragment A Impact


NOTE: Click on the images to view them at their highest resolution.

Short Description of the A Sequence

This sequence of six images shows the A impact of 16 July 1994. These images were taken at the German-Spanish 3.5 meter telescope on Calar Alto in southern Spain, using MAGIC, the near infrared camera of the Max-Planck-Institut fuer Astronomie in Heidelberg, Germany.

The bright object to the right of Jupiter is the innermost Galilean moon, Io, and the fainter oval structure in the southern hemisphere is the Great Red Spot. The polar caps appear bright at the wavelength of the observations, 2.3 um, which was selected to maximize contrast between the impact region and the jovian cloud deck. All six frames have a logarithmic relation between intrinsic brightness and colour, which mimics the behaviour of the human eye.

The following paragraphs give further information on each image.

Pre-Impact 19:49:04 UT (upper left)

Jupiter and Io twenty minutes prior to the first impact. The spikes emerging from Io are due to diffraction from the secondary mirror support structure. The two small dots to the northwest (upper right) of the moon are multiple reflections from the methane absorption filter used to darken the planetary disk.

A Impact Precursor 20:11:30 UT (upper middle)

A faint dot appears on the southeast limb of Jupiter, just below the Great Red Spot. This is the impact precursor, which occurs 5-7 minutes before the main brightness peak. Note that Io is approaching Jupiter in its orbit around the giant planet.

Start of Main Peak 20:16:27 UT (upper right)

The explosion of impact is clearly underway. Within a couple of minutes, the point of light brightened to levels which forced us to shorten the exposure time to avoid saturating the detector in MAGIC.

Maximum Brightness 20:23:25 UT (lower left)

At maximum brightness, the explosion due to fragment A was brighter than Io. This frame has approximately 1/4 the exposure time of the others, and hence appears more grainy due to lower signal to noise ratio.

Io Setting 20:42:02 UT (lower middle)

The impact site has grown to a scar bigger than planet Earth within minutes of maximum brightness. Io is just disappearing behind the limb of Jupiter.

40 Minutes Post-Impact 20:49:31 UT (lower right)

Io has disappeared and the Great Red Spot is near the central meridian. The impact structure now appears double due to the blanket of ejecta to the southwest (lower right) of the main site. This ejecta blanket also appears in the previous frame.

Picture Credits:

Tom Herbst, Max-Planck-Institut fuer Astronomie, Heidelberg, Doug Hamilton, Max-Planck-Institut fuer Kernphysik, Heidelberg, Hermann Boehnhardt, Universitaets-Sternewarte, Muenchen, and Jose Luis Ortiz Moreno, Instituto de Astrofisica de Andalucia, Granada.

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