Eros

Eros (433 Eros) is a near-Earth asteroid and the second-largest member of the Amor group, with dimensions of roughly 34 × 11 × 11 km — making it shaped like a curved potato or peanut. It orbits the Sun at a mean distance of 1.46 AU, with a perihelion of 1.13 AU that brings it inside the orbit of Mars but not quite to Earth's orbit. Eros is an S-type asteroid with a stony composition of silicates and some metal. It was the first near-Earth asteroid ever discovered and the first asteroid to be orbited and landed on by a spacecraft. Its elongated shape and tumbling rotation produce dramatic brightness variations visible from Earth.

Eros is typically faint (magnitude 11–15), but during close approaches to Earth it can brighten dramatically — reaching magnitude 7 or even brighter during rare favorable oppositions, making it visible in binoculars. Its next very close approach will occur in January 2056, when it may reach magnitude 6.7. When bright, Eros can show rapid motion against the stars and noticeable brightness changes over hours due to its elongated shape and 5.27-hour rotation period. Check ephemeris data for upcoming apparitions. At typical magnitudes of 11–13, a 6-inch or larger telescope is needed. Its near-Earth orbit means it can appear in any part of the sky.

Eros was discovered on August 13, 1898, independently by Gustav Witt in Berlin and Auguste Charlois in Nice. It was the first known near-Earth asteroid, and its close approaches were used for decades to improve measurements of the astronomical unit (the Earth-Sun distance). In February 2000, NASA's NEAR Shoemaker spacecraft entered orbit around Eros, returning over 160,000 images during its year-long mission. On February 12, 2001, NEAR Shoemaker gently touched down on Eros's surface — the first spacecraft landing on an asteroid — continuing to transmit data for over two weeks from the surface.