Heres something I stumbled across on the web.

"Subaru" is the Japanese word for the star cluster Pleiades that is depicted in the company logo. The Pleiades (also known as the Seven Sisters) has only six stars easily visible to the naked eye. Subaru's logo of six stars represents the five companies that came together after World War II to form one large company. This word translated from Japanese to English means: Unite.

Before WWII, the maker of SUBARU cars, Fuji Heavy industries (FHI), was known as Nakajima Aircraft, which made many fighters and bombers. Even the famous Mitsubishi Zero fighter had a Nakajima 14 cylinder engine. After the war, the company was forced to spread into 15 companies to cut the strength of the huge weapon industry. In the early 1950s, five of the original companies gathered into one again to restart as a transportation company. That was FHI and explains the five little stars and one big star.

So, the present SUBARU emblem represents the present company structure rather than the original star cluster image.