The Przybylski’s star

An extraterrestrial civilization could be using “their local star as a repository for radioactive fissile waste material.”

Is an extraterrestrial civilization dumping their nuclear waste onto their home star? Credit: image generated by OpenAI’s DALL·E.

The following is an excerpt from my upcoming book “A Story of More Than 5000 Worlds — An Insight Into The Possibility of Life Beyond Earth”.

What if a technological advanced extraterrestrial civilization is capable (and keen) of using their home star to dispose of their nuclear waste?

This is something researchers Daniel Whitmire, and David Wright suggested in an article[i] that appeared in 1980 in the Icarus planetology magazine then directed by Carl Sagan. Such a capability could be used by the extraterrestrial civilization to keep their home planet free from such wastes or as a way of advertising their presence to the rest of the universe.

Colloquially known as “star salting”, this hypothetical practice has been suggested as a strong technosignature. According to the current understanding of stellar processes, if this is happening somewhere in the universe for a given star, astronomers would see very distinctive traces of elements that should not be present in the spectra of the star.

What do I mean by “elements that should not be present”?

Stars generate their energy through nuclear fusion, starting with the fusion of hydrogen into helium and progressing through to heavier elements like iron. Thus, it is common to find a mixture of elements, including iron, in most stars. However, heavy elements such as promethium, with a half-life of less than 20 years, and plutonium, with a half-life of up to 24,000 years, are not expected to be found in large quantities in a star. These elements, if present, should be in small portions as they would have decayed long ago given the extensive ages of stars. A significant presence of such elements in a star might indicate chemical or nuclear processes that are still unknown, or a replenishing mechanism that continues to add those elements to the star. In summary, a typical star should contain large quantities of iron. However, heavier elements than iron are expected to be found only in very small quantities.

Fusion occurs in stars due to enormous temperatures and pressures within their cores. Credit: USA Department of Energy — Office of Science

Well, brace for it. There is a star that exhibits quite the opposite of what is expected: very low traces of iron and large quantities of heavy elements.

The star HD 101065, which is better known as the Przybylski star, was discovered by the Polish-Australian astronomer Antoni Przybylski (1913–1985) in 1960.[ii]

Its peculiar spectrum continues to challenge our understanding of stellar physics and has many researchers scratching their heads.

The Przybylski’s star, located at approximately 310 light-years from Earth, is categorized as an Ap-type star; the ‘p’ in the name of this category stands for “peculiar”. Ap-type stars rotate slower than regular type-A stars, which favors the reliable measurement of their chemical composition.

Multiple hypotheses have been proposed to explain the unusual spectrum of the Przybylski’s star. Following the concept of Occam’s razor, which indicates that the simplest explanation is most likely correct (and also the most boring in this case), the most likely explanation is that the measurements are just wrong and somehow the presence of these heavy elements is due to some misinterpretation of the data.

If you are not too much into the ‘misinterpretation of data’ explanation, a few more exciting alternatives have been proposed. One of them is the proposition of an “island of stability”. This idea suggests that super heavy elements, still yet to be observed in nature, exist, and could decay into the elements astronomers observe in the spectrum of the Przybylski’s star.

Another hypothesis suggests the presence of a neutron star companion that is “contaminating” the Przybylski’s star’s atmosphere. Due to the immense pressures and temperatures present in a neutron star, elements heavier than iron are likely to be present. Unfortunately, nothing seems to indicate the presence of such a companion object.

An artist impression of a star and its neutron star companion. This has been suggested as a possible explanation for what is being observed in the Przybylski’s star. Credit: Elisa Schösser — Universe Today

This leaves us with the possible explanation that an extraterrestrial civilization is involved. As suggested by Whitmire and Wright in their 1980 article, an extraterrestrial civilization could be using “their local star as a repository for radioactive fissile waste material.” If that is the case, such a practice would cause changes in the stellar spectrum of the star over long periods of time.

Something that everyone agrees on is that more data and more studies are needed. The understanding of what is happening with this star can have a profound impact on our understanding of stellar and chemical processes, and potentially on the life as we know it as well.

References

[i] Whitmire, Daniel P., and David P. Wright. “Nuclear waste spectrum as evidence of technological extraterrestrial civilizations. Icarus 42, no. 1 (1980): 149–156.

[ii] Przybylski, A., 1961. HD 101065 — a G 0 Star with High Metal Content. Nature, 189(4766), pp.739–739.