Tag Archives: Comet SL9

Where Were You on the Nights of July 16th to 22nd, 1994?

If you were an amateur astronomer back then with access to just about any kind of telescope, there is only one answer to the title question (unless you were clouded out) – observing Jupiter.

This was because a barrage of 26 comet fragments, the mortal remains of Comet Shoemaker-Levy 9, impacted Jupiter on those dates.  Since this was a truly unprecedented event, every telescope on Earth that could observe Jupiter (amateur or professional) and just about every spacecraft with a telescopic camera was pointed at the giant planet.

Before we get too much further into the story, here is a bit of background for readers who were either not born then or were too young to know what the fuss was about at the time.  In the 1920s, a small, unknown comet wandered a bit too close to Jupiter.  As a result, the comet wound up orbiting Jupiter.  Nobody on Earth at the time knew this was happening.  For decades, this comet was a rather odd satellite of Jupiter.  Then, one day in the early 1990s, the orbit of the comet was shifted and it got extremely close to Jupiter, so close that the gravitational pull of Jupiter on one side of the comet was stronger than that on the other side.  As a result, the comet broke apart into 26 large fragments.

Shortly after the breakup, Carolyn Shoemaker and David Levy were working on a project to search for near-Earth objects (NEOs).  Conditions were not too good for observing and they had a piece of questionable film.  Rather than toss it and give up on the evening, they decided to take an image near Jupiter.  When the exposure was processed, they discovered a comet.  Assuming it was a run-of-the-mill comet, the discovery was reported to the Central Bureau of Astronomical Telegrams (CBAT).  Upon further scrutiny, the comet appeared peculiar and elongated.  This soon led to the discovery that the comet was a train of fragments.  Then the orbit calculations came in.  These revealed that the comet was in orbit around Jupiter and that it would hit the planet in July of 1994.  Refinements in the calculations revealed that the impacts would take place on the side of Jupiter facing away from Earth.  While this was initially disappointing, it was soon realized that the impact sites would rotate into view from Earth rather quickly.  But there was still the question of whether there would be anything to see.  Back in the early 1980s, the late Carl Sagan predicted that anything impacting Jupiter would disappear beneath the clouds without a trace.

As the date approached, there was a near-total mobilization of astronomers, both amateur and professional.  After the first impact, it was soon apparent that Sagan was wrong.  Each impact left a dark blotch on the clouds of Jupiter.  Not only that, the blotches lasted for weeks and gradually faded.

In my 6-inch F/8 newtonian reflector, the blotches looked like bullet holes in Jupiter.  I’m sure that no amateur who has seen them has forgotten them.

On this anniversary, Space Daily ran a short little article in their “Jovian Dreams” section.  However, it just focused on the professional observations.  No mention was made of the amateur experience.

I remember this event.  Do you?