- August 14, 2019 - Planétarium Rio Tinto Alcan : Astronomical News
It’s rare for astronomers to be able to witness a cosmic collision in the solar system. That’s what happened in July 1994, when the comet Shoemaker-Levy 9 slammed into the planet Jupiter.
The story begins in an unremarkable way in the spring of 1993, when astronomers Carolyn and Eugene Shoemaker, along with Montrealer David Levy, were observing the sky with a telescope at the Palomar Observatory in California, looking for comets or asteroids approaching close to the Earth.
A surprising discovery
On the evening of March 24, 1993, helped by a French student, Philippe Bendjoya, our trio discovered a comet on one of their photographic plates. It was the ninth comet discovered by these astronomers. But the shape of this new comet struck them as strange. Rather than appearing as a round and unclear spot, the Shoemaker-Levy 9 comet presented an elongated, flattened shape. It seemed to show more than one core!
Comet specialists set to work to understand how a celestial body could take on such an appearance.
It quickly turned out that the comet was not in orbit around the Sun like all the others, but around the planet Jupiter instead.
Numerical simulations by astronomers indicated that the comet passed close to Jupiter in the 1970s and was captured by it. Then in 1992, the comet passed so close to the planet that it broke up into 21 fragments. Further, everything indicated that those fragments were going to disintegrate later in Jupiter’s atmosphere, between July 16 and 22, 1994. For the first time in history, astronomers would observe at first hand a collision between two heavenly bodies in the solar system.
Every effort would be made so that nothing of the phenomenon was missed. In addition to ground-based telescopes, artificial satellites were used to record the cosmic collisions. Unfortunately, the collisions took place on the face of Jupiter not visible from the Earth. It would be necessary to wait several minutes to observe the result of the impacts.
The pictures were spectacular! The fragments entered the atmosphere at a speed of 200,000 km/h. The first impact created a dark cloud of dust 6,000 km in diameter, while the biggest left a scar 12,000 km long.
The dust left by the disintegration of the fragments could be observed for months, allowing astronomers to better understand the dynamics of planet Jupiter’s atmosphere.
Jupiter, a celestial defense shield
Following the collision, astronomers realized that Jupiter was protecting the inner planets of the solar system, including the Earth, from a number of catastrophic impacts. Its substantial gravity attracts, most of the time, heavenly bodies like comets before they venture into the inner areas of the solar system. Thus, Jupiter protects us against devastating collisions.