Asteroid taxonomy.

The spectral reflectivity of asteroid surfaces over the wavelength range of 0.3 to 1.1 μm can be used to classify these objects into several broad groups with similar spectral characteristics. The three most recently developed taxonomies group the asteroids into 9, 11 or 14 different classes, depending on the technique used to perform the analysis. The distribution of the taxonomic classes shows that darker and redder objects become more dominant at larger heliocentric distances, while the rare asteroid types are found more frequently among the small objects of the planet-crossing population.