trapezium mill sbmhayphillips. Trapezium Cluster, The Trapezium or Orion Trapezium Cluster, also known by its Bayer designation of Theta 1 Orionis, is a tight open cluster of stars in the heart of the Orion Nebula, in the constellation of OrionIt was discovered by Galileo GalileiOn February 4, 1617 he sketched three of the stars (A, C, D), but ...