Notes from Under Sky

A Map of the Trapezium

A guide to the lettered stars of the Trapezium

The above is a map of the lettered stars of the Trapezium, the light source for the Great Orion Nebula (Messier 42). North is up, east is left. Unlike most multiple stars, the Trapezium stars are not labelled in order of brightness. The first four stars are labelled in order of increasing right ascension; after that, the ordering is roughly in order of increasing magnitude.

Stars A through D run from fifth to eighth magnitude and should be visible through any decent telescope at a magnification above about 30x or so. E and F are about 11th magnitude. Stars this dim would ordinarily be visible in a 60 mm scope, but because they are fairly close to A and C, respectively, a larger scope is usually needed to observe them, although optical quality and steady seeing are the paramount concerns. They have been detected in apertures as small as 55 mm.

Stars G and HH (a double) are about 16th magnitude and can only be seen in the largest amateur telescopes, probably at least 16 inches or larger.

Copyright (c) 1999 Brian Tung