The Stars of the Trapezium

This is probably the best know multiple stars in the sky. It is also one of the most interesting for the small telescope. In many double star catalogs it has become customary to designate the fours stars A, B,C, and D in order of fight ascension rather than in the usual order of brightness. The star called C is the true primary of the group with a visual manitude of about 5.4. Star D is the second in brightness at 6.3. A is third at about 6.8. The fainest star, B, is an eclipsing binary with a period of 6.471 days. In 1975, Star A was also identified as an eclipsing binary with a period of 65.432 days. ( Burnham's Celestrial Handbook, V2, p1327).

The 11th magnitude stars E and F are a well know observational challenge to amateur astronomers who often use them to judge the quality of the seeing as well as the quality of their telescopes. They have been observed with aperatures of under 3 inches on nights of very good seeing. They become and easy target for telescopes of 10 inches of aperature or more.

Photographing E and F is an even more interesting challenge. Both of these dim stars are seperated from their brighter companions by only 4". The exposure duration required to record the 11 magnitude stars combined with the distortion created by atomospheric seeing generally cause the two fainter stars to become part of the blob of the brighter stars. This effect can be seen in the image at the top of the page. However, the task is not impossible.....

This image of the Trapezium six was taken with a SBIG ST-7 CCD camera attached to a Celestron C11 SCT telescope. The image is the sum of three 0.3 second exposrures and has been enlarged by 3x.