Comets leave a trail, and they are not very big (like 6 miles across for the main body). How can they persist long enough to have a recurring 4000 year orbit?
Halley's Comet repeats every 75–76 years and is (most recently) just a bit more than 3 miles diameter. Either it started out really, really a lot larger, or it hasn't been on the same orbit for all that long. Anyway, bravo!