closest approach of a comet to Earth

The closest recorded encounter of a comet with Earth was that of Comet Lexell in 1770. Its least distance from Earth was 0.015 astronomical units or 2.244 million km on 1st July 1770. This is about six times the distance of the Moon. When at its closest, the apparent size of the coma was nearly five times the diameter of the full Moon. The comet was discovered by Charles Messier on 14th June 1770, but it was subsequently named after A. J. Lexell who studied the orbit of the comet and published his results in 1772 and 1779. He found that the comet had been projected into its Earth- approaching orbit by a close encounter with Jupiter 1767. Another even closer approach to Jupiter in 1779 once again perturbed the comet's orbit drastically, and it has been unobservable from Earth since then.