In West Africa, specifically Mali, lives a tribe of people called the Dogon. The Dogon are believed to be of Egyptian decent and their astronomical lore goes back thousands of years to 3200 BC. According to their traditions, the star Sirius has a companion star which is invisible to the human eye and this companion star has a 50 year elliptical orbit around the visible Sirius and is extremely heavy. It also rotates on its axis. Two French anthropologists, Marcel Griaule and Germain Dieterlen recorded it from four Dogon priests in the 1930's. How did a people who lacked any kind of astronomical devices know so much about an invisible star? The star, which scientists call Sirius B, wasn't even photographed until it was done by a large telescope in 1970.
The Dogon stories explain that also. According to their oral traditions, a race people from the Sirius system called the Nommos visited Earth thousands of years ago. They also appear in Babylonian, Accadian, and Sumerian myths. The Egyptian Goddess Isis, who is sometimes depicted as a mermaid, is also linked with the star Sirius.