Sirius B

The companion was found by arithmetic before anyone looked at it. In the 1840s Friedrich Bessel, measuring the motion of Sirius across the sky with great precision, found that it did not move in a straight line but wavered, and concluded that it must be orbiting a common centre with something unseen and massive. That is a striking inference to publish about an object nobody could detect. It was observed in 1862 by Alvan Graham Clark while testing a new telescope, appearing as a faint point almost lost in the glare of its companion. For half a century after that it was simply a very dim star, and the puzzle was why an object of substantial mass should be so faint.

The answer came from its light. Spectra obtained in the early twentieth century showed the companion to be hot and white rather than cool and dim, which meant the faintness could only be explained by an extremely small surface, and therefore by a density unlike anything then known. It became the defining example of the class of collapsed stellar remnants now called white dwarfs, an object about the mass of the sun compressed to roughly the size of the earth, and later measurements of the shift in its light provided an early test of general relativity.

The star's place in esoteric literature rests on one ethnographic report. In 1950 two French anthropologists published an account of a Dogon cosmological system in Mali that, they reported, included a small heavy invisible companion of Sirius with a long orbital period. The report was taken up in the 1970s in a widely read book proposing that the knowledge could only have come from contact with visitors from that system, and the claim has circulated ever since. The report was tested by later fieldwork.

An anthropologist who worked among the Dogon over a long period, and who set out specifically to check the earlier findings, reported that he could find no such star knowledge among the people he worked with, that the elaborate system described appeared to be unknown, and that the earlier accounts may reflect the questions asked as much as the answers given. He also noted that the astronomical facts had been widely reported in the European press decades before the fieldwork. The atlas records the position as contested. The dispute is between anthropologists over the conduct and interpretation of fieldwork, and nothing in it is a judgment on the Dogon, who are a living people and whose actual cosmology is a matter for the ethnography rather than for the literature built on it.

Sources Un systeme soudanais de SiriusMarcel Griaule and Germaine Dieterlen with The Sirius MysteryRobert K. G. Temple, Dogon Restudied: A Field Evaluation of the Work of Marcel GriauleWalter E. A. van Beek