aszteroida

An asteroid is a small rocky body that orbits the Sun. Most are remnants from the early solar system that never formed into a planet. The largest concentration lies in the main asteroid belt between Mars and Jupiter, though a significant number travel near Earth or share an orbit with larger planets as Trojans.

Size ranges from meters to hundreds of kilometers across. The largest object in the belt is the dwarf planet Ceres, about 940 kilometers in diameter; other large asteroids include Vesta, Pallas, and Hygiea. Asteroids are classified by composition and reflectivity into types such as carbonaceous (C-type), silicaceous (S-type), and metallic (M-type). C-types are dark, S-types are brighter, and M-types are metal-rich. They can be rocky, metallic, or a mix, and some show evidence of past geological activity on their surfaces.

Most asteroids have irregular shapes and rotate with periods from a few hours to about a day. Orbits typically lie in the main belt with semi-major axes between roughly 2.1 and 3.3 astronomical units from the Sun. Near-Earth asteroids have orbits that bring them close to Earth; Jupiter and other planets also host Trojan asteroids sharing an orbital path with the planet.

Asteroid science began with telescopic observations in the 19th century and continues through spacecraft missions. Notable missions include Dawn, which orbited Vesta and Ceres; Hayabusa2, which visited Ryugu; and OSIRIS-REx, which collected samples from Bennu. Data from these missions inform models of solar-system formation and planetary defense.

Naming and designation are governed by the International Astronomical Union. Most asteroids are named by their discoverers following IAU guidelines, often after mythological figures, scientists, or other cultural figures.