4055 Magellan, provisional designation 1985 DO2, is a bright and eccentric vestoid asteroid of the Amor group of near-Earth objects, approximately 2.5 kilometers in diameter. It was discovered by American astronomer Eleanor Helin at Palomar Observatory on 24 February 1985.
Being a V-type asteroid, it is thought to have originated from the Rheasilvia crater, a large impact crater on the south-polar surface of 4 Vesta, which is the main-belt's second-most-massive asteroid after 1 Ceres.
Magellan orbits the Sun at a distance of 1.2–2.4 AU once every 2 years and 6 months (897 days). Its orbit has an eccentricity of 0.33 and an inclination of 23° with respect to the ecliptic. The first observation was made at the Australian Siding Spring Observatory, extending the asteroid's observation arc by just one month prior to its discovery observation at Palomar. It has a minimum orbital intersection distance with Earth of 0.2404 AU (36,000,000 km).
According to observations by the Keck Observatory and to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures between 2.2 and 2.8 kilometers in diameter and its surface has a high albedo of 0.31 to 0.33. The Collaborative Asteroid Lightcurve Link (LCDB) agrees with the Keck observations, adopting an albedo of 0.31 and a diameter of 2.49 kilometers.
Between 2000 and 2015, six rotational light-curves for this asteroid were obtained from photometric observations by astronomers Petr Pravec and Brian D. Warner, as well as by the Mexican Asteroid Photometry Campaign and the Palomar Transient Factory. The highest rated light-curve by LCDB's standards was obtained by French amateur astronomer David Romeuf in July 2015, which gave a rotation period of 7000748202000000000♠7.48202±0.0001 hours with a brightness variation of 0.45 magnitude (U=3). The large variation suggests an elongated shape.
The minor planet was named after Portuguese navigator and explorer Ferdinand Magellan (Fernão de Magalhães; c. 1480–1521), who led and died on the first circumnavigation of the Earth during 1519–1522. The minor planet is also named after the modern Magellan spacecraft, which was launched by NASA in 1989 and went on to map the surface of Venus. The Portuguese navigator is also honored by the craters Magelhaens on Mars and Magelhaens on the Moon. Naming citation was published on 2 December 1990 (M.P.C. 17466).