H Impact Sequence, 18 July 1994

This is a six image sequence showing the collision of fragment H of 
Comet Shoemaker-Levy 9 with Jupiter. The frames were taken over a three 
hour period on the 18th of July, 1994, using the MAGIC infrared camera 
on the 3.5 meter telescope on Calar Alto. The star-like object next to 
Jupiter is the largest Galilean moon, Ganymede. The polar caps and 
pre-existing impact sites appear bright at the wavelength of 
observation, 2.3 microns, which was selected to maximize contrast 
between the impacts and the jovian cloud deck. 

The following paragraphs give further information on each image. 

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Pre-Impact 19:28 UT (upper left) 

Jupiter and Ganymede approximately four minutes prior to the impact of 
fragment H. The bright feature near the southern polar cap is the impact
site of the D and G fragments, which struck the planet 32 and 12 hours 
earlier, respectively. Note the crescent shaped ejecta blanket to the 
southwest (lower right) of the D/G site. 

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Second Impact Precursor 19:33 UT (upper middle) 

The second and brighter of two impact precursors observed at Calar Alto.
The first precursor appeared approximately two minutes earlier, and the 
main peak of the H impact began roughly four minutes after this 
exposure. 

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Approaching Maximum Brightness 19:40 UT (upper right) 

The main peak of the H impact approaches maximum light. The explosion 
brightened for another 4 minutes, during which time the MAGIC camera 
acquired near infrared spectra of the event. These spectra give strong 
indications of hot (>2000 K) molecular gas. 

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Impact Site Appears 19:54 UT (lower left) 

The fragment H impact site rotates into view. The scar on Jupiter's 
atmosphere is now larger than the planet Earth. Spectra taken just 
before this image show that the site has cooled considerably. 

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Ejecta Blanket 20:19 UT (lower middle) 

Appearance of the ejecta blanket. Forty five minutes after impact, the H
collision site shows a second feature to the southwest. This is the 
crescent-shaped ejecta blanket similar to that seen in the pre-existing 
D/G site. Ganymede is just beginning its transit across the face of 
Jupiter. 

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Aftermath 22:40 UT (lower right) 

The H impact site joins its brethren. More than three hours after 
impact, Ganymede has completed its transit, and the H impact site has 
rotated past the meridian and lies just to the southwest (lower right) 
of the Great Red Spot. This image was taken with the telescope pointed 
near the horizon, and the greater thickness of Earth's atmosphere 
renders the picture somewhat fuzzy. Nevertheless, the crescent-shaped 
ejecta blanket is obviously similar to that of the D/G impact (see 
adjacent frames). The sites visible on Jupiter are from left to right: 
A, E/F, H, and D/G (on the western limb). 

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.