The Trapezium, Theta 1 Orionis, is the most famous multiple star system in the night sky. Located at the very heart of M42, the Orion Nebula, it is one of the youngest star clusters known. Its age is estimated to be less than a million years old and is located at a distance of 1,337 light-years. North is to the top in the above image. The four brightest stars in the Trapezium (A, B, C and D) are easily visible in a four-inch telescope with decent optical quality under good seeing conditions. They range in brightness from magnitude 5 to magnitude 8. All are hot class O and B stars.