Rolling mouse over image displays SDSS colors of each asteroid.
Explanation: The dots show the distribution of 33,000 asteroids observed by Sloan Digital Sky Survey (SDSS). The x- and y-axes are the semi-major axis and proper inclination (roughly speaking, the distance from the Sun and the height above the orbital plane) computed by Milani and Knezevic, and listed in ASTORB file compiled by Bowell. The dots are colored according to their measured SDSS colors (note that these colors do not correspond directly to asteroid colors as would be seen by the human eye because SDSS sensitivity extends to infrared range). A striking feature of this figure is the color homogeneity and distinctiveness displayed by asteroid families, which are seen as clumps (this is how they are defined). Their distinctive optical colors indicate that the variations in chemical composition within a family are much smaller than the compositional differences between families, and strongly support earlier suggestions that asteroids belonging to a particular family have a common origin. For more details, please see a paper "Color Confirmation of Asteroid Families" by Ivezic et al. (Astronomical Journal, November 2002).
Moving the cursor over the image displays SDSS colors of each asteroid.