Comet Shoemaker–Levy 9

E. Shoemaker, D. Levy

Shoemaker- Levy 9 ( SL9 also briefly ) got its name because it was the ninth short-period comet that was discovered by Carolyn and Eugene Shoemaker along with David H. Levy. Its official name is D/1993 F2 ( Shoemaker- Levy ). The "D " in his name stands for the English " disappeared " ( "disappeared" ) and indicates that the comet no longer exists. His fragments smashed on the planet Jupiter in July 1994.

Discovery

The comet was first detected on a photo that was taken in California on 24 March 1993 with a 46 -cm Schmidt telescope at Mount Palomar Observatory. The Japanese Shuichi Nakano said the anticipated clash first advance. The observation was subsequently confirmed by other astronomers. It quickly became clear that it was an unusual comet: He was probably located close to the planet Jupiter, and was broken into several fragments.

Orbit

Probably as early as the 1960s came the comet under the strong gravitational forces of Jupiter and was forced as a quasi- satellite in a highly elliptical orbit around the planet Jupiter. As a result, he passed in July 1992 Jupiter within the Roche limit. Due to the tidal forces broke the comet may have had originally a diameter of about 4 km, in 21 fragments between 50 and 1000 m size, strung on a multi-million -kilometer-long chain. The fragments having the letter "A" were to "W " refers to the differentiation. (The letters "I" and "O" has not been used because of their similarity with the digits "1" and "0". )

Because of its proximity to Jupiter, the orbit of the comet was subject to large disturbances. The orbital elements listed in the adjacent table describe the orbit of the comet in May 1993 from heliocentric view: With a semi-major axis of 5.16 AU, an eccentricity of 0.07 and an inclination of 1.4 ° the orbit of Jupiter was ( semi-major axis 5.20, eccentricity 0.05, orbital inclination 1.3 ° ) are very similar, especially since the comet was indeed "captured " by Jupiter. In the view of Jupiter, the comet ( > 0.99 eccentricity) moving on a highly elliptical orbit at a distance of up to 0.33 AE around the planet.

Just two months after the discovery showed the orbit determination of the astronomers that the comet pieces would collide in July 1994 with the planet Jupiter.

Impact on Jupiter

Between 16 July and 22 July 1994, the fragments of the comet Shoemaker- Levy 9 hit Jupiter's southern hemisphere in at a speed of 60 km / s, and put it the energy of 50 million Hiroshima bombs (which have an explosive power of about. 13 kT TNT had ) free. This was the first time that the collision of two bodies of the solar system and the effects of such impact event could be observed directly.

Although the impact point from the earth point of view just behind the " edge " was Jupiter and thus was not directly visible, the astronomers were able to so-called " Plumes " ( hot gas bubbles, similar to a " mushroom cloud " ) seen rising over the edge of Jupiter. Due to the rapid rotation of Jupiter, the impact sites were visible only a few minutes after the Impakten from Earth. It was found that up to 12,000 km had left in the atmosphere of Jupiter dark spots with diameters that remained visible for months.

Only the Galileo spacecraft was able to observe the Impacts directly from a distance of 1.6 AU. Due to a defective satellite dish the capacity of the spacecraft for data transmission, however, were limited, and it could not be delivered, all measured values ​​to the earth. In addition to that Galileo was sent as a result of the Challenger disaster with only three years late to Jupiter - the start date would have been held in 1986, the spacecraft would have to track the impacts from close in Jupiter orbit.

In the spectra of the Plumes large amounts of molecular sulfur were (S2) and carbon disulfide (CS2 ) found more than by the explosion of a relatively small comet nucleus could be released. It is believed the origin therefore in the deeper layers of the atmosphere of Jupiter. Other proven molecules are carbon monoxide (CO ), ammonia ( NH3) and hydrogen sulfide (H2S). Also emission lines of iron, magnesium and silicon were observed: The heat of the explosions must therefore have been sufficient to evaporate these metals. Water was observed in lesser quantities than had been initially expected. Presumably, the water molecules were broken down by the heat.

The collision was observed not only by astronomers who ausschöpften almost all available opportunities to observe Jupiter this week, but pursued in the mass media with great interest.