Zdenek Sekanina Zdenek Sekanina Zdenek Sekanina (born 12 June 1936, Mladá Boleslav, Czechoslovakia (now Czech Republic)) is a Czech-American astronomer and scientist. In 1959, Sekanina started to study astronomy at Charles University in Prague, where he was graduated in 1963. Since 1980, he has been working at the Jet Propulsion Laboratory. His main areas of professional study are meteors and interplanetary dust as well as the study of comets. In the course of his investigations, he dealt with Halley's comet, the Tunguska event, as well as the break-up and impact of Comet Shoemaker–Levy 9 on Jupiter. He was involved in the data
Comet Shoemaker–Levy 9 Despite published predictions, astronomers had not expected to see the fireballs from the impacts and did not have any idea in advance how visible the other atmospheric effects of the impacts would be from Earth. Observers soon saw a huge dark spot after the first impact. The spot was visible even in very small telescopes, and was about (one Earth radius) across. This and subsequent dark spots were thought to have been caused by debris from the impacts, and were markedly asymmetric, forming crescent shapes in front of the direction of impact. Over the next six days, 21 distinct impacts