Complex sentence: The entire group includes about 40 stars, with ten of the brightest ones forming the well-known coathanger figure, a straight line of six stars and a "hook" of four stars.
Split into simpler sentences: The entire group includes about 40 stars, with ten of the brightest ones forming the well-known Coathanger figure. The Coathanger itself is formed by a straight line of six stars and a "hook" of four stars.