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 ..

Hubble Space Telescope observations of the Trapezium region

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Hartmut Frommert
Christine Kronberg
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Last Modification: April 13, 2006