The Przybylski's star is the weirdest and, so far, most unexplained star humans have discovered, after the Tabby star about which I have already written.
It lies 356 light-years from Earth, is 40% more massive than the Sun, and is named after a Polish astronomer who discovered it in 1961. Its bizarre nature comes from what we discovered it contains: an abundance of heavy elements, including ones that only have short-lived isotopes, which shouldn’t exist in a star about 1.5 billion years old. Such elements exist for only a few years or less. Furthermore, this star contains lower-than-expected amounts of elements such as iron or nickel.
It’s an enigma where these elements come from, and it's even sparked speculation about alien involvement. Supposingly, this star could be a nuclear waste disposal system for an advanced technological civilization.
Without involving extraterrestrials, there are some options where these elements might come from, but none fully explain what is going on.
Maybe this star swallowed a chunk of waste from neutron star mergers. It could consist of very heavy elements, which are created during kilonovas, the rapid neutron capture or the r-process. These are rare events that synthesize vast amounts of elements such as gold, platinum, uranium, and even heavier atomic nuclei. Perhaps they decay within the Przybylski’s star, and we see the products of this decay. Supernovas can also create debris enriched with high superheavy elemental content. Perhaps this star swallowed some debris from a supernova.
This star is very magnetic. Perhaps this helps sort its elemental content into layers. In this view, Przybylski's star is not weird in its content, but in the distribution of its composition, and what we can detect from Earth are the products of radioactive decay of its bizarrely arranged layers.
One of the more fascinating explanations for the weirdness of this star is that it offers evidence that the nuclear island of stability exists. As we discover more and more heavy elements and their isotopes with more and more neutrons, they are increasingly short-lived, but there is a theory that at some point further out on the Mendeleev elemental table, beyond the heaviest known so far, exist superheavy isotopes with longer half-lives.
The Tabby star, which has mysteriously dimmed on short time spans, recently took all the spotlight, but the Przybylski’s star is equally or even more enigmatic, and we genuinely have no idea what causes its peculiar characteristics. It might be an entirely new phenomenon in science about which we have no idea yet.