Comet Shoemaker–Levy 9 When the comet passed Jupiter in the late 1960s or early 1970s, it happened to be near its aphelion, and found itself slightly within Jupiter's Hill sphere. Jupiter's gravity nudged the comet towards it. Because the comet's motion with respect to Jupiter was very small, it fell almost straight toward Jupiter, which is why it ended up on a Jove-centric orbit of very high eccentricity—that is to say, the ellipse was nearly flattened out. The comet had apparently passed extremely close to Jupiter on July 7, 1992, just over above its cloud tops—a smaller distance than Jupiter's radius of ,
David H. Levy biography of Pluto-discoverer Clyde Tombaugh in 2006, and his tribute to Gene Shoemaker in "Shoemaker by Levy". He has provided periodic articles for "Sky and Telescope" magazine, as well as "Parade Magazine", "Sky News" and, most recently, "Astronomy Magazine". Periodic comets that Levy co-discovered include 118P/Shoemaker–Levy, 129P/Shoemaker–Levy, 135P/Shoemaker–Levy, 137P/Shoemaker–Levy, 138P/Shoemaker–Levy, 145P/Shoemaker–Levy, and 181P/Shoemaker–Levy. In addition, Levy is the sole discoverer of two periodic comets: 255P/Levy and P/1991 L3. On February 28, 2010, Levy was awarded a Ph. D. from the Hebrew University of Jerusalem for his successful completion of his thesis "The Sky in Early Modern English Literature: A Study