For Aboriginal Australians, the stars helped locate them in both time and place. New research has shown they also noticed changes in brightness in at least three stars, keeping an oral record unlike any other known in the world.
Many people have made fools of themselves attributing impossible scientific knowledge to ancient peoples – for example, Jordan Peterson's discredited claims that ancient cultures solved DNA's structure. However, Dr Duane Hamacher of Monash University is making a much more credible, although still impressive, claim.
Without advanced telescopes, there was no way for Indigenous Australians to know the stars now called Betelgeuse (Alpha Orionis), Aldebaran (Alpha Tauri) and Antares (Alpha Scorpii) are all red super giants, some of the largest stars in our region of the Milky Way. However, all three drew their attention for their brightness and deep red color, a product of having cooled as they expanded to hundreds of times the Sun's diameter.
Aristotle decided the stars were unchanging in their brightness, and Western astronomers took this for granted until 1596 when the variation of Mira was tracked. However, it seems others were paying closer attention.
Hamacher, who has brought the astronomical traditions of Aboriginal Australians to wider attention, has presented evidence in the Australian Journal of Anthropology that several South Australian tribes not only noticed the variation but kept alive an oral tradition.
Many Indigenous Australians described Orion and the Pleiades very much like the ancient Greek myth – a mighty hunter named Nyeeruna chasing a group of seven sisters. In some parts of the continent, Aldebaran and the Hyades, known together as Kambugudha, were considered the oldest sibling, protecting the younger sisters from Orion's lust.
Hamacher noticed something anthropologists missed, however. Some of these tales refer to rises and falls in the strength of Nyeeruna’s “fire lust”, represented by Betelgeuse, something we now know happens on a 1.1-year cycle. Similarly, Kambugudha's capacity to withstand Nyeeruna's threat is represented as altering with Aldebaran's brightness.
Oral traditions of the lower Murray region also refer to a red star, Waiyungari, whose lust grows and fades. Waiyungari's brightest periods act as a reminder to curtail sexual activity. This story was recorded in 1935 by anthropologist Norman Tindale, who concluded Waiyungari is Mars – not the best news as Mars makes its closest approach for 15 years over the next few months.
However, Hamacher notes Antares is a bright and very red variable star with peaks in brightness roughly every 4.5 years. It fits with what we know of the Waiyungari story much more closely and indeed was quite close to Mars in the sky when Tindale was doing his research, increasing the chance of confusion.
Sadly, centuries of colonization have destroyed any details that might have been useful for tracking changes in these stars, whose variations are still not fully understood.
Nevertheless, Hamacher argues the work “highlights the importance of considering and examining Indigenous oral traditions around the world for descriptions of celestial phenomena that can aid both astrophysicists and social scientists in their understanding of oral tradition, cultural astronomy, and Indigenous Knowledge Systems.”
The only other known example of a pre-telescopic culture observing changes in stellar brightness (eruptions aside) comes from Egypt. However, this was not a variable star in the normal sense, but the binary star Algol, which dims when one of its components passes in front of the other.
However, Hamacher's claim is not incredible. A subsequent paper in the Journal of Astronomical History and Heritage by Bradley Schaefer of Louisiana State University showed even inexperienced observers can notice the variation in each of these stars' brightness if they compare them to nearby stable stars of similar brightness.