In China's ancient books, Beidou is composed of Shu Tian, Tian Xuan, Tianji, Tianquan, Yuheng, Kaiyang and Yaoguang. The ancients connected these seven stars and imagined them as barrels of wine in ancient times. In the west, they are the seven bright stars at the tail of Ursa major (at least to the naked eye).
Shu Tian is a red giant with a short life span of only about 4 million years. Tian Xuan is also a main sequence star with a life span of about 70 million years. Tian Ji is almost the same as Tian Xuan. Tianquan is small and its life span is about 500 million years. Yuheng is about 4 million years ago. Kaiyang is about 70 million years ago. Eta Ursa major has a life span of less than 2.7 million years. The above data are estimated values and are for reference only.