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Trapezium in orion was a very strange quadruple star

  1. Jan 11, 2006 #1
    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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  3. Jan 12, 2006 #2


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  4. Jan 12, 2006 #3


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    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. (?)
    Last edited: Sep 18, 2006
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