A class of asteroid, fairly common in the outer main asteroid belt, with a distribution that peaks at a mean distance from the Sun of 4.0 AU. Members of this class have a featureless reflectance spectrum, flat to slightly reddish over the wavelength range 0.3–1.1 μm. Their spectra are intermediate between classes C and D. P-class asteroids are distinguished from the spectrally identical E and M classes by their lower albedos (0.02–0.06). Members of this class include (87) Sylvia, diameter 261 km, and (153) Hilda, diameter 171 km.
Subjects: Astronomy and Astrophysics.