111P/Helin–Roman–Crockett

Comet Helin–Roman–Crockett is known for making extremely close approaches to Jupiter being a quasi-Hilda comet.^[7] During these approaches, it actually orbits Jupiter.^[8] The last such approach was in 1976,^[3] the next will be in 2071.^[3] The Jovian orbits are highly elliptical and subject to intense Solar perturbation at apojove which eventually pulls the comet out of Jovian orbit for the cycle to begin anew.

Simulations predict such a cycle is unstable, the object will either be captured into an encounter orbit (e.g. Shoemaker-Levy 9) or expelled into a new orbit which does not have periodic approaches. This implies that 111P's orbit is recent within the past few thousand years.

Estimates for the size of its nucleus in 2004 place it roughly about 1.2 km (0.75 mi) in diameter.^[6] Follow-up studies in 2007 generally agree with this estimate, and depending on the comet's activity involved, the comet is likely somewhere between 0.92–2.78 km (0.57–1.73 mi) in diameter.^[9]