Comet Shoemaker-Levy 9 Impacted Jupiter 25 Years Ago

Comet Shoemaker-Levy 9's Impact against Jupiter was a sensational astronomical phenomenon.

July 16, 2019, marks 25 years since Comet Shoemaker-Levy 9 (S-L9) impacted the largest planet in our solar system; Jupiter.

The cosmic phenomenon that occurred in the summer of 1994 gave astronomers the very first direct observation of an extraterrestrial collision between objects in the solar system, which was predicted by astronomers.

This generated great coverage in the media to such an extent that Shoemaker-Levy 9 became popular and was observed by astronomers from all over the planet given its scientific importance.

In addition, the impacts provided new information about Jupiter and highlighted its role in reducing space debris from the inner solar system. In other words, it was then when scientists confirmed theories that Jupiter acts as an umbrella, shielding the inner solar system from potentially apocalyptic, planet-ending space rocks.

Jupiter in infrared, Shoemaker–Levy 9 collision (left), Io (right). Public Domain.
Jupiter in infrared, Shoemaker-Levy 9 collision (left), Io (right). Public Domain.

Discovered by Carolyn and Eugene Shoemaker and David Levy, the comet was discovered on the night of March 24, 1993, in a photograph taken with the camera of Schmidt Palomar Observatory in California (USA), becoming the first observed comet orbiting around a planet instead of the Sun, something quite unusual at that time.

In July of 1992, the SL9 orbit passed the Roche limit of Jupiter and the tidal forces pressed to destroy the comet, which was later observed as a series of 23 fragments up to 2 kilometers in diameter, which ended up colliding with the southern hemisphere of Jupiter between July 16 and 22, 1994 at a speed of approximately 60 kilometers per second.

Tracing back the comet’s orbital motion revealed that it had been orbiting Jupiter for some time. It is likely that it was captured from a solar orbit in the early 1970s, although the capture may have occurred as early as the mid-1960s.

Shoemaker–Levy 9, disrupted comet on a collision course. (total of 21 fragments, taken on May 17, 1994). Public Domain.
Shoemaker-Levy 9, disrupted comet on a collision course. (total of 21 fragments, taken on May 17, 1994). Public Domain.

Each shock generated a scar, that is, a dark spot, each of which was more visible than the Great Red Spot and remained there for several months.

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As explained B. G. Marsden,  “Comet Shoemaker-Levy (1993e)” Comet Shoemaker-Levy 9 was the ninth periodic comet (a comet whose orbital period is 200 years or less) discovered by the Shoemakers and Levy.

It was their eleventh comet discovery overall including their discovery of two non-periodic comets, which use a different nomenclature.