How are asteroids classified?
Asteroids are classified according to their ‘albedo’ which means their reflectivity. The majority of asteroids fall into the following three categories: C-type (carbonaceous): Includes more than 75 percent of known asteroids. Very dark with an albedo of 0.03-0.09. Composition is thought to be similar to the Sun, depleted in hydrogen, helium, and other volatiles. C-type asteroids inhabit the main belt’s outer regions. S-type (silicaceous): Accounts for about 17 percent of known asteroids. Relatively bright with an albedo of 0.10-0.22. Composition is metallic iron mixed with iron- and magnesium-silicates. S-type asteroids dominate the inner asteroid belt. M-type (metallic): Includes many of the rest of the known asteroids. Relatively bright with an albedo of 0.10- 0.18. Composition is apparently dominated by metallic iron. M-type asteroids inhabit the main belt’s middle region.
