“It’s worthwhile to not just do what was done 60 years ago, but also to keep an eye out for very unusual things,” says SETI Institute astronomer Seth Shostak. “The universe has been around for three times as long as the Earth has been around, so there could be aliens out there that are very, very much more advanced than we are—not just 1,000 years, but millions and billions of years ahead.”
Enigmatic Exotic Chemical Composition
It’s been said that the discovery of cosmic anomalies don’t begin with ‘eureka!’; they begin with “that’s funny…” In 1960 a Polish-Australian astronomer Antoni Przybylski using a telescope to study fast-moving stars in southern skies said “no star should look like that,” when he made an amazing discovery that came to be known as “Przybylski’s Star” –a mysterious object located some 370 light years away from the Earth now known as HD 101065, in the constellation of Centaurus with a unworldly, exotic chemical composition, that takes almost 200 years to fully rotate on its axis.
Przybylski’s enigma is a variable star whose spectrum shows it laced with bizarre elements like europium, gadolinium, terbium and holmium, iron and nickel in unusually low abundances, and short-lived ultra-heavy elements, actinides like actinium, plutonium, americium and einsteinium that should not be able to persist in the atmosphere of a star that out Przybylski’s Star in the Ap class of chemically peculiar stars.
Ultra Heavy Elements Baffle Astronomers
The existence of these ultra heavy elements has baffled astronomers for decades. A neutron star, observes Paul Glister in Centauri Dreams, is one solution, a companion object whose outflow of particles could create heavy elements in Przybylski’s Star, and keep them replenished. The solution, he writes “seems to work theoretically, but no neutron star is found anywhere near the star.” In new paper, Vladimir Dzuba at the University of New South Wales and colleagues suggest that the actinides in Przybylski’s Star are evidence of the slow decay of superheavy elements.
A New Isotope?
The idea, writes Glister, “is that there may be a so-called island of stability involving elements with 114 or more protons in their nuclei, super-heavy elements that nonetheless are long-lived. If these exist, then the short-lived plutonium, einsteinium and the rest found in the star would simply be decay products. We may be, in other words, about to discover a new isotope not produced as a fleeting sample in an experiment but as an element observed in nature. That in itself is not unusual Penn State’s Jason Wright reminds us that helium was first found in the Sun.”
The Answer: An Extraterrestrial Civilization?
Astrophysicist Wright, reports Glister, “raises the point that advanced civilizations might use stars to store nuclear waste, a notion broached by Daniel Whitmire and David Wright as far back as 1980, and considered as well by Carl Sagan and Iosif Shklovskii in their Intelligent Life in the Universe. Whitmire and Wright even opined that the most likely stars in which we would find such pollution were late A stars like Przybylski’s Star.”
“Przybylski’s Star is my favorite astrophysical enigma (this coming from the guy notorious for making Tabby’s Star famous!),” writes Wright in his Penn State blog, AstroWright, famous for having bizarre abundance patterns. “Not like: ‘oh look, the carbon-to-oxygen ratio is greater than one’; more like this star has more praseodymium than iron. Yeah. How could that be?!, Wright asks.
“First off,” Wright says Przybylski’s star is an Ap star. That’s “A”, with a note “p” meaning “peculiar” (which is an astrophysical understatement.)
Ap Stars Break All the Rules
Ap stars break all the rules, observes Wright. “They have intensely strong magnetic fields, and as a result they don’t rotate fast (presumably having slowed down long ago), and as a result they have very narrow lines, and as a result you can see all of the spectral features of the elements in their atmosphere.” Why? he asks.
“I’ve never seen a good answer as to why Ap stars have strong fields, Wright remarks. “They could be primordial or generated from a dynamo, says Wikipedia, which is fine but misses the weird part: regardless of where the field comes from, why do only a minority of A stars have such fields? What’s different about them?”
“And here’s the even weirder thing: the abundances of the elements that we get to see thanks to the slow rotation are way off of the abundance patterns we see elsewhere in the universe. Why?”
Most of the lines in Ap stars, notes Wright “would also be iron, though perhaps of the ionized variety (since they’re too hot for neutral iron). Not so; in fact for a long time Antoni Przybylski wondered if his eponymous star even had any iron; its abundance is down by a factor of at least an order of magnitude from the Sun’s. Instead, Przybylski found lots of other elements in his weird star: strontium, lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium… stuff you rarely hear mentioned outside of a Tom Lehrer song. Now, these things should be only present in the tiniest of abundances, not the most easily seen lines in the atmosphere! What’s going on?”
Is the Answer Levitation?
The answer seems to be levitation, says Wright: Apparently it’s what puts the “p” in “Ap,” –“the bulk star does not have weird abundances, but its upper atmosphere does because the upper layers of the star are differentiated and stratified!”
“But that’s not what’s so weird about Przybylski’s star,” Wright exclaims. “No, that star doesn’t just have weird abundance patterns; it has apparently impossible abundance patterns. In 2008 Gopka et al. reported the identification of short-lived actinides in the spectrum. This means radioactive elements with half-lives of order thousands of years (or in the case of actinim, decades) are in the atmosphere.
“What?! The only way that could be true is if these products of nuclear reactions are being replenished on that timescale, which means… what exactly? What sorts of nuclear reactions could be going on near the surface of this star?
Jason Wright’s Three Solutions
Wright concludes that are three proposed solutions he’s aware of. “The first is about 8 years old; the second, he says. is brand new and a ‘huge if true’ sort of exciting idea. The last is quite fanciful and has never, so far as I can tell, gotten past a journal referee (if anyone’s even tried to publish it), but sort of dials the ‘huge if true’ up to 11.
The first: Neutron Stars. In 2008, shortly after identifying the “impossible” elements in Przybylski’s Star, Gopka et al. proposed a solution: the star has a neutron star companion. Neutron stars have strong winds of positrons and electrons that bombard the heavy elements in the atmosphere of the star, transmuting them to the elements we see. The big problem with this is that these are sharp lines, so we can measure radial velocities to Przybylski’s Star, and it does not have a short period neutron star companion.
The second: Flerovium, Unbinilium, Unbihexium. According to Wikipedia, notes Wright, “many physicists think [these isotopes’ half-lives] are relatively short, on the order of minutes or days.Some theoretical calculations indicate that their half-lives may be long, on the order of 109 years. Enter Dzuba, Flambaum, and Webb, who propose that the source of the short-lived actinides in Przybylski’s Star is one of these isotopes! As the isotope decays, its daughter products—all less massive than it but still actinides—are visible in the star before they decay away. There would be some steady-state concentration dictated by the lifetime of the isotope. They propose the parent isotope could be 298Fl, 304Ubn, or 310Ubh. But where would it come from? Dzuba et al. suggest that it might be the product of a supernova explosion, like other neutron-heavy elements. Its half life could be short enough that it would be present in a young A star but very rare on the Earth—or perhaps you need a certain kind of supernova to make it, and one of those wasn’t in the mix that generated the elements that make the Earth. If so, it could be common in other stars and planets, but just very hard to detect in anything other than an Ap star with levitation.”
The Third: Aliens. The last of the three solutions I’m aware of, says Wright, sotto voce, whispered but never published, is that it’s the product of artificial nuclear fusion. “Here on Earth, he notes, people sometimes propose to dispose of our nuclear waste by throwing it into the Sun.” In fact, he notes, “seven years before Superman thought of the idea, Whitmire & Wright (not me, I was only 3 in 1980) proposed that alien civilizations might use their stars as depositories for their fissile waste.They even pointed out that the most likely stars we would find such pollution in would be… A stars! (And not just any A stars, late A stars, which is what Przybylski’s Star is). In fact, back in 1966, Sagan and Shklovskii in their book Intelligent Life in the Universe proposed aliens might “salt” their stars with obviously artificial elements to attract attention.”
As Harvard’s Avi Loeb has concluded, coming to Wright’s rescue: The existence of advanced extraterrestrial life is no more speculative than extra dimensions or dark energy.
Image credit: Shutterstock License