Day of the Comet
The Impact of Comet Shoemaker-Levy 9 with Jupiter
Comet Shoemaker-Levy 9 (SL9), torn into pieces because of a close approach to Jupiter in July 1992, collided
with Jupiter during the third week of July 1994. The impacts of the cometary fragments released more energy into
Jupiter's atmosphere than all of Earth's nuclear arsenals. Because the impacts occurred on the back side of Jupiter,
as seen from Earth, the explosions were not directly observable from telescopes on Earth or the Hubble Space Telescope.
However, Galileo, because of its unique vantage point in space to the side of Jupiter, was able to view the direct
impact sites of the comet pieces.
The breakup of a comet into many fragments is an unusual event but the collision of a large comet with a planet
is an extraordinary event that probably only happens once in a millennium. The fact that we had a spacecraft,
Galileo, with the perfect birds-eye view of Jupiter at the time that this happened was nothing short of lucky.
Galileo had just finished its encounter with asteroid Ida when the news came in that SL9 was going to collide
with Jupiter. There was a lot of controversy whether this would make a "big splash" or a "big fizzle."
Lucky for us, the science team decided to go ahead and do some observations. The timing was tricky, but thanks
to efforts worldwide, Galileo was able to get some fantastic and unique views of the events. Check out the award-winning
SL9 homepage for lots of information and links to pictures.
 How did the comet
get its name?
 Comet Shoemaker-Levy 9 was so named
because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. It was
first detected on a photograph taken on the night of March 24, 1993 with a telescope on Palomar Mountain in California.
How did
scientist know that it was going to run into Jupiter?
The comet was first observed in March
1993. Later observations from Earth-based telescopes were used to demonstrate that the comet was in orbit about
Jupiter, and had made a very close approach (within 1.4 Jupiter radii from Jupiter's center) on July 7, 1992. During
this close approach, the unequal Jupiter gravitational attractions on the comet's near and far sides broke the
comet apart. By studying the orbit of the comet and its predicted flight path, scientists found that the comet
was likely to hit Jupiter in 1994.
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