Theta1 Orionis: The Trapezium Cluster in the Orion Nebula M42

Open Cluster Trapezium Cluster, in the Orion Nebula M42 (NGC 1976), in Orion

[M42 detail, AAT 29]
Right Ascension 05 : 35.4 (h:m)
Declination -05 : 27 (deg:m)
Distance 1.6 (kly)
Visual Brightness 4.0 (mag)
Apparent Dimension 47 (arc min)

Discovered by Galileo Galilei in 1617.

The first recorded observation of a multiple star character of Theta1 Orionis, the bright stellar object in the Orion Nebula (M42), occurred on February 4, 1617, when it was observed and recorded as triple by Galileo Galilei (Galileo 1617, Fedele 1949, Ondra 1999, Mosher 2005), who did, however, not recognize the Orion Nebula due to unknown reasons.

With Galileo's observation generally unrecognized, Theta1 Orionis independently revealed as triple star and described by Christiaan Huygens in 1656 (Huygens 1659). The fourth component, Theta1 Orionis B, was found by Abbe Jean Picard in 1673 to complete the "Trapezium." The fourth Trapezium star was independently recovered by Christiaan Huygens in 1684.

The Trapezium Stars:

Star             HD     RA  (2000.0) Dec      m_v    M_v   Sp      RV  Names

41 Theta1 Ori A 37020 05:35:15.8 -05:23:11 6.73v -5.0 O7 +33 V1016 Ori 41 Theta1 Ori B 37021 05:35:16.1 -05:23:04 7.96v -4.4 B0V +24 BM Ori 41 Theta1 Ori C 37022 05:35:16.5 -05:23:23 5.13v? -6.6 O6pe +28 HR 1895 41 Theta1 Ori D 37023 05:35:15.8 -05:23:13 6.71 -4.1 B0.5Vp +31 HR 1896
41 Theta1 Ori E 41 Theta1 Ori F 41 Theta1 Ori G 41 Theta1 Ori H

.. more to come soon ..

  • The Trapezium through the Galilean Telescope, Tom Pope and Jim Mosher

  • Jean-Claude Mermilliod's WEBDA cluster page for the Trapezium cluster in the Orion Nebula, M42
  • SIMBAD Data of the Trapezium
  • Publications on the Trapezium Cluster (NASA ADS)


  • More images of the Trapezium Cluster
  • The Trapezium Region of M42 investigated from Lowell Observatory
  • Infrared Observations of the Trapezium Cluster region in M42
  • Hubble Space Telescope observations of the Trapezium region

    Hartmut Frommert
    Christine Kronberg

    [SEDS] [MAA] [Home] [Back to M42] [PNG]

    Last Modification: April 13, 2006