BM Orionis

This is the "B" star, or the Northern-most star of the famous Orion Trapezium in the famous Orion Nebula M42. You will need a small telescope to see it. I actually noticed its brightness change before I know it is a variable star. On 1998/12/27 4:20 UT, BM was so dim that it disappeared from the Trapezium. According to Burnham's Celestial Handbook, BM Orionis is an eclipsing binary with a period of 6.471 days, and the magnitude ranges from 8.0 -- 8.7. Yes, you can feel the 0.7 magnitude difference!