Assertion: period comet | /r/HasProperty | interstellar visitors
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Source sentences:
text: Tom Hands, an astrophysicist at the University of Zurich’s Institute for Computational Science and his co-author Walter Dehnen at Ludwig Maximilian University of Munich used mathematical models to estimate just how many long-period comets—those that take 200 years or longer to circle the Sun—could be interstellar visitors.