Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. D/1770 L1, popularly known as Lexell's Comet after its orbit computer Anders Johan Lexell, was a comet discovered by astronomer Charles Messier in June 1770. It is notable for having passed closer to the Earth than any other comet in recorded history, approaching to a distance of only 0.015 astronomical units. The comet has not been seen since 1770 and is currently considered a lost comet. The comet was discovered on June 14, 1770, in the constellation Sagittarius by Messier, who had just completed an observation of Jupiter and was examining several nebulae.