We see from the earth Sirius, the Dog-star, move in a bit disorder, of which earlier scientists inferred there would be an invisible companion star, whose gravitation might make Sirius move on elliptical orbit in the Universe. Several decades after it, owing to development of science and technology, scientists found the star's companion Sirius B, the Pup, which has mass roughly equal to the Sun though has only the size roughly equal to the Earth, then which has large density and gravity but is invisible to the naked eyes, whose color is white and whose gravitation they verified effects on the orbit of Sirius. This discovery was in 19th century. By the way, there is an African tribe who have a mythology about Sirius. The Dogons in Mali. The fact that Sirius is an important star for the Dogons is not amazing because that is explained by the prominent brightness of Sirius, but according to French anthropologists, astonishingly, the Dogons knew already the existence of the compa