Trapezium in orion was a very strange quadruple star

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i always thought the trapezium in orion was a very strange quadruple star - not a double binary, but an actual quadruple star group with bizarre orbital patterns. however, now i read that it is just a cluster, i guess implying that they are not really orbitally associated. can someone please provide the correct description of the trapezium for me? thanks.
 
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Interesting question, see here for more: http://www.space.com/scienceastronomy/astronomy/hot_stars_001110.html
 
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jnorman said:
i always thought the trapezium in orion was a very strange quadruple star - not a double binary, but an actual quadruple star group with bizarre orbital patterns. however, now i read that it is just a cluster, i guess implying that they are not really orbitally associated. can someone please provide the correct description of the trapezium for me? thanks.
In smaller telescopes you can see the four main stars in the trapezoid shape, hence the name, which are just as you said, a small cluster of non-associated stars, not a triple, quadruple, etc. star system. In a decent 6" scope under good seeing conditions you can see also two more stars for a total of 6. The main four are simply labled A, B, C, and D. The two fainter stars easily seen in a decent 8" scope are labled E and F. There are also two fainter stars in the group labled G and H, but they are very faint at magnitude 16.
A is a variable star that ranges from mag. 6.8 to 7.7. B is an actual eclipsing binary at mag. 7.9. C and D are mag. 5.1 and 6.7 respectively and E and F are both mag. 11.0.
Any group of stars that forms an identifiable pattern but are not a constellation or a bound star system is called an asterism. So, I guess asterism is the description you are looking for. I have a neat JPEG of the system with positions and magnitudes listed, but I'm not sure I know how to post a small photo here. (?)
http://en.wikipedia.org/wiki/Asterism_(astronomy)
 
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