An Etymological Dictionary of Astronomy and Astrophysics
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A star cluster located in the center of the → Orion Nebula whose four brightest stars form the vertices of a trapezoid. They are known as θ¹ Ori A, B, C, and D and are of magnitude 6.7, 8.0, 5.1, and 6.7 respectively. They are packed in an area 22 arcseconds across (10,000 A.U.). The Trapezium stars are responsible for the illumination of the entire Orion Nebula. The principal and the most massive star of the group is θ¹Ori C, a young main sequence → O star of type O6. The three others are → B stars. Almost all of the Trapezium stars are multiple: the most massive star θ¹Ori C is double, the next massive star θ¹Ori A is triple, θ¹Ori B is at least quadruple, and θ¹Ori D is apparently single.

→ trapezium; → cluster.