The Ages and Dimensions of Trapezium Systems

MK spectral types and memberships were obtained for 120 stars in 31 systems thought to be Trapezium systems. Twenty-eight optical components were found, after the removal of which, 17 systems are hierarchical and three have no companions. Practically all of the remaining Trapezium systems are either the same age or younger than the Hyades, i.e., less than 10 to the 8.9th years old. The maximum radii of Trapezium combined with hierarchical systems exhibit a dramatic decrease with primary spectral type or age T, ranging from about 50,000 AU for OB primaries to 1000 AU for G dwarfs. If stars have an observed binary separation of about 5000 AU, it is unlikely that the sun would have a stellar companion at 92,000 AU. A Ba II star with a physical companion, a star with strong double Ca II emission lines, and a chance projection of a nearby quadruple hierarchical system on a distant triple hierarchical system is discussed.