Heinrich Louis d'Arrest
July 13, 1822 – June 14, 1875
Heinrich Louis d'Arrest was a Prussian astronomer, born in Berlin.
While still a student at the University of Berlin, d'Arrest was party to Johann Gottfried Galle's search for Neptune. On September 23, 1846, he suggested that a recently drawn chart of the sky, in the region of Urbain Le Verrier's predicted location, could be compared with the current sky to seek the displacement characteristic of a planet, as opposed to a stationary star. Neptune was discovered that very night.
D'Arrest's later work at the Leipzig Observatory led him, in 1851, to the discovery of the comet named for him (formally designated 6P/d'Arrest). He also studied asteroids (he discovered 76 Freia) and nebulae.
He won the Gold Medal of the Royal Astronomical Society in 1875.
The crater D'Arrest on the Moon is named after him, as well as a crater on the Martian satellite Phobos and the asteroid 9133 d'Arrest.