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
Lexell's Comet The comet was also noted by several other astronomers. The comet was observed in Japan. Surviving records identify it as an astronomical and historical phenomenon. It was observed in the Hejaz in Safar 1184 AH (June 1770), where some believed it to be the comet predicted by the poet al-Fasi, portending future events. On July 1, 1770, the comet passed 0.015 astronomical units from Earth, or approximately 6 times the radius of the Moon's orbit. Charles Messier measured the coma as 2° 23' across, around four times the apparent angular size of the Moon. An English astronomer at the time