12216

12216 is a main-belt asteroid that was discovered on 5 April 1990 by astronomer S. Torres at the Siding Spring Observatory in Australia. The asteroid was first observed as part of the 6-month program to identify new minor planets. Its provisional designation was 1990 HD, and it was formally numbered 12216 by the Minor Planet Center after its orbit could be determined with sufficient accuracy. The discovery was announced in the Minor Planet Circulars in July 1990, and the object was subsequently observed multiple times over the next decade, allowing its orbital elements to be refined.

The asteroid orbits the Sun with a semi-major axis of approximately 2.8 AU, placing it in the outer region of the main asteroid belt between Mars and Jupiter. Its orbital period is about 4.7 years, with an eccentricity of 0.12 and an inclination of 7.3 degrees relative to the ecliptic. These parameters classify 12216 as an S-type asteroid, indicating a stony composition rich in silicate minerals. The estimated diameter of the asteroid is roughly 7 kilometers, based on an absolute magnitude of 13.5 and an assumed albedo of 0.20. Photometric observations have revealed a rotation period of 8.9 hours, suggesting a relatively stable spin axis and a fairly uniform shape.

The asteroid was designated with the minor planet number 12216, but it has not been given a formal name as of the latest observations. It is listed in the Jet Propulsion Laboratory's Small-Body Database and the International Astronomical Union's Minor Planet Center database, where it remains cataloged for continued study and to aid in the broader understanding of asteroid belt dynamics and composition.