Sarah Zielinski writes in The Smithsonian that Jupiter, as the largest planet in our solar system, occasionally pulls comets into its orbit. Sometimes, as with comet Shoemaker-Levy 9 in 1994 (pictured), Jupiter's gravity will even pull a comet into a direct impact. Zielinsky writes:
Astronomers from Japan and Northern Ireland, presenting their findings today at the European Planetary Science Congress, used observations of Comet Kushida-Muramatsu—from when it was discovered in 1993 and when it returned in 2001—to calculate the comet’s path over the previous century. They determined that the comet became a temporary moon when it entered Jupiter’s neighborhood in 1949. It made two full, if irregular, orbits around the planet, and then continued its travels into the inner solar system in 1962.
The researchers also predict that Comet 111P/Helin-Roman-Crockett, which circled Jupiter between 1967 and 1985, will again become a temporary moon and complete six loops around the planet between 2068 and 2086.
“The results of our study suggests that impacts on Jupiter and temporary satellite capture events may happen more frequently than we previously expected,” David Asher of Northern Ireland’s Armagh Observatory told the AFP.