21167

21167 is a numbered minor planet in the central main asteroid belt. The object was discovered on 12 March 1997 by the Lincoln Near‑Earth Asteroid Research (LINEAR) survey at the Socorro Observatory in New Mexico, United States. It was first observed on 6 May 1997 and the orbit has since been refined over more than 15 years of observation.

The orbit of 21167 has a semi‑major axis of approximately 2.55 astronomical units (AU), an eccentricity of 0.09, and an inclination of roughly 8° relative to the ecliptic. These orbital elements place it firmly within the inner part of the main belt, where its period around the Sun is about 4.08 Earth years. The asteroid’s orbit crosses no planetary orbits, and it is currently classified as a non‑resonant background population asteroid.

Photometric data from the Lowell Observatory and the Minor Planet Center indicate a light‑curve amplitude of about 0.25 magnitudes, with a rotation period near 4.2 hours. The light‑curve asymmetry suggests a somewhat elongated shape. No close approaches or significant gravitational perturbations have been recorded since its discovery.

Spectral classification based on visible–near infrared data suggests an affinity with C‑type or Cb‑type asteroids, implying a carbonaceous composition and a relatively low albedo. Using an assumed geometric albedo of 0.15, the diameter of 21167 is estimated to be around 7 kilometers, though direct measurements from radar or thermal infrared observations are not yet available.

21167 has not been given a formal name and remains designated by its provisional designation 1997 … until it meets the criteria for naming set by the International Astronomical Union. The asteroid continues to be tracked by celestial mechanics databases to refine its orbital parameters and to monitor for any potential future missions or observational campaigns.