Przybylski’s Star IV: Or…

Part IV of III.  Part I is here.

A coda: Howard Bond correctly points out that my three explanations are only necessary if a very plausible and less interesting explanation is wrong (a caveat that I had in an early draft of my posts but edited out unintentionally.)

The identification of short-lived actinides could be a mistake! The Gopka et al. identification of these lines was made in a journal I had not heard of, Kinematics and Physics of Celestial Bodies, apparently originally in Russian. As far as I can tell, the paper has been cited exactly once, by the Dzuba et al. paper that proposed the metastable heavy isotope.

The journal and language of the Gopka et al. paper aren’t necessarily problems, of course, but they do raise eyebrows. The fact that it has not been cited could mean that the paper was simply not read (not surprising, given the journal), or that everyone who studies the star that saw the paper decided it was not worth citing, even to refute it.

[Edit: Steinn is much better at this than I am.  He points me to a 2003 AAS abstract by Crowley et al. supporting the existence of short-lived isotopes, a topic Howard Bond also mentioned on Facebook to me. Steinn also finds this paper and this one which I think I missed because I didn’t realize that promethium, a lanthanide, has no isotopes with half-lives longer than 20 years.

The Mkrtichian paper I linked to in the last post mentions Bidelman et al. PASPC, 336, 309, as supporting the short-lived isotope interpretation, and conference proceedings by Yushchenko, Gopka, & Goriely that ADS doesn’t know. Goriely discusses mechanisms here.

So the claim is stronger than I originally hedged in this post.  It’s put best in this followup paper by Crowley it al., originally shown to be by Brian Davis (but which I only just found again, now that I’m thinking of Pm): “The spectroscopic evidence is strong enough that we would declare promethium to be present without hesitation, if any of its isotopes were stable.”  In their other words, it’s only the strong prior against finding unstable isotopes that makes them hedge.]

The mystery of Przybylski’s Star is still a very good one if there are no short-lived actinides isotopes in the spectrum—the identification of the stable lanthanides seems quite secure and fascinating and it remains the most peculiar of the peculiar A stars—but it would mean that it is much more plausible that technical but mundane explanations for the star exist.

[P.P.S. There is now a part V/III about prior art by Drake and Shklovskii.]

11 thoughts on “Przybylski’s Star IV: Or…

  1. jtw13 Post author

    Greg:

    Saying Andromeda has moons is not an extraordinary claim, but saying they are detectable today is. Saying ETIs exist is not an extraordinary claim. Saying that they are detectable and you have found them is.

    Falsifiability is essential to science, but not to truth claims (unless you’re a strict positivist). It’s fine to assert things you can’t prove or don’t have much evidence for in general (society couldn’t function otherwise), but the standard is higher in the scientific literature.

    It’s true, though, that the community seems to have a much higher tolerance for data-free speculations about string theory, inflation, fifth forces, and dark matter particles than detectable alien civilizations, and that’s unfortunate and inappropriate.

  2. Greg

    I can understand three of those, but I don’t understand why extraterrestrial intelligence is seen as an extraordinary claim. If I said there were no moons in Andromeda, that would be a far more extraordinary claim than claiming that it has a similar proportion of moons to planets that our own galaxy has. It would be strange if the physical process that produced moons in our solar system just didn’t happen in Andromeda, or even in far places in our own galaxy that we’ll probably never be able to check for moons.

    Intelligent life is something that we unambiguously know is possible. It’s the end product of a bunch of chemistry that we don’t understand yet. It’d be really strange if Earth were just so special that it’s the only place where a tool-using intelligent species evolved. Attributing any specific astronomical anomaly to intelligent life is still a bad idea, but it feels like it’s regarded as only slightly more plausible than the notion that demons are trying to trick us by changing spectral patterns, and is less plausible than the notion that there’s some spooky new physics involved.

    Falsifiability also worries me a bit. If Paul Steinhardt is right to call inflation (and its consequence, the multiverse) unfalsifiable, then it seems like it’s entirely possible that the scientific method could rule out explanations that are true. Lawrence Krauss has said that in the distant future, the wavelength of the CMB will be too long to be physically observable due to the universe’s expansion, and proper application of the scientific method will lead to conclusions that are wrong. Falsifiability isn’t a standard we can do away with without psuedoscience becoming ‘science’ despite being complete BS, but it worries me that the standard can lead to rejections of truth.

  3. jtw13 Post author

    Thanks for that!
    http://www.smbc-comics.com/comic/2011-06-11

    I’m not sure what you’re asking in terms of the essay; I only lightly moderate the comments (mostly keeping spam out) so if you want to post something go ahead. It would probably make more sense to post it yourself (get a blog, or use Medium) and then link to it.

  4. AC DeBlanc

    I think this discussion is drifting toward Z. Weinersmith’s essay of 06-11-2011(1). The point he makes is telling. May I post an essay on the topic on this site?

    Thanks.

    Ref: (1) Saturday Morning Breakfast Cereal of the date given.

  5. jtw13 Post author

    It a combination of things.

    The first is that the ETI (extraterrestrial intelligence) hypothesis is very hard to test absent some sort of clear signal because we don’t know how to model alien behavior. With out a test or model, it’s not really a scientific hypothesis.

    The next is Sagan’s adage “extraordinary claims require extraordinary evidence”

    The next is that we don’t want to engage in “aliens of the gaps” thinking; since aliens could have arbitrarily advanced technology (and, so, be essentially “magical” by Clarke’s Third Law) we could ascribe almost anything we don’t understand to them.

    Finally, no one wants to cry wolf. The media eats this stuff up and blows it out of proportion, so you don’t want to go around saying “maybe its aliens” often or loudly or else you just become Ancient Aliens guy (“I’m not saying it’s aliens…”). It’s a narrow path to walk.

  6. Greg

    As a layperson, there’s something that keeps confusing me when I see discussions of this sort. Why are artificial origins seen as so unlikely in these circumstances? We unambiguously know that life-producing technology exists in the universe. By contrast, when strange things like this come up, it looks like we can’t always say with certainty that the natural explanations that come up are physically possible. It would strike me as bizarre if we were the only species in the galaxy that had ever produced technology.

    Not saying I’m a fan of the ‘OMG little green men’ hypothesis, I just don’t get why it should be regarded as so outlandish. Is it just because aliens show up constantly in fiction, or am I missing something important?

  7. AC DeBlanc

    Don’t get me wrong. To paraphrase Gus Grissom from “The Right Stuff”, the issue here ain’t superheavies, it’s curium. Superheavies are, as you pointed out, hard to identify. They may also be very scarce. It looks to me like ground states of nuclides on decay chains which end beta decay in the superheavy region don’t fission, but that tells me very little. I’ve found a little bit about how r-process nuclides grow, but there isn’t much information handy about excited states of superheavy element precursors. We do know that heavy isotopes of Fm fission with millisecond half-lives, and we know that Md260, a doubly-odd nuclide, decays mainly by fission. An r-process path capable of making superheavy elements probably exists, but it’s equally plausible that the path includes some attrition due to fission. I’d more or less expect superheavy elements to be rare.

    Consider curium by contrast. We know curium can form in an r-process, because we’ve done just that. It should be, to a first approximation, nearly as abundant as uranium. Its lines are well characterized. It should be an easy target. Since any process short of black magic which forms superheavies should form curium at the same time and in greater abundance, curium suffices as evidence of one mechanism by which Pm has found its way to the “surface” of Przybylski’s star,

    Thanks.

  8. jtw13 Post author

    AC wrote: “Its spectrum doesn’t show any lines for superheavies, or we would have heard about it, big time.”

    Not at all! There are many unidentified lines in the spectrum, and we don’t know what the spectra of superheavies look like, because we’ve never seen them and the energy levels are too complicated to calculate precisely.

  9. AC DeBlanc

    Sorry about the grammar. Its spectrum doesn’t show any lines for superheavies, or we would have heard about it, big time. Elements anchored by N=184 will probably be around, but not enough of them to make usable lines. What I’m going to have to do is give the literature an amateur-grade scouring for curium, though. If there’s enough Cm in the star’s “surface” to show reliable spectral lines, there will be plenty of fission daughters, including Pm, forming in those same locations.

    Thanks.

  10. jtw13 Post author

    Thanks for that. Why do you write “I know the spectrum of Przybylski’s star doesn’t contain superheavy elements”? I don’t know which elements it contains for sure (I haven’t studied the literature at that detail), but there are many, many unidentified lines.

  11. AC DeBlanc

    I’ve looked at the r process, using KUTY data from a presentation by Dr. Koura and Moller-Nix data from LANL. Unless I’m way off, Z > 113 isn’t likely to form. There’s a fission barrier between fresh r-process nuclides and the zone of beta stability. Superheavy elements will be around for a while, but they’re not necessary. Curium 250 has a half-life of almost 10000 years and decays principally by spontaneous fission. Other r-process actinides also have both strong fission branches and long half lives. Fission products will include promethium. Unless actinide daughter abundances are weird, that’s the tough element to explain. I know the spectrum of Przybylski’s star doesn’t contain superheavy elements, but does it show curium? If curium is there, is it possible Przybylski’s star collided with a fresh supernova remnant some time ago?

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