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This question is kind of a companion question to this question on the creation of heavier elements via head on stellar collision. Both arise from me thinking about Przybylski's Star. This star has short-lived elements, the shortest of which of is einsteinium, with the longest lived isotope of that element having a half-life of only 472 days. So, the question is, how is it still there? And, I read one explanation somewhere was that even heavier elements were decaying into einsteinium. So, my question is, would we be able to tell if heavier undiscovered elements were in a star's spectral lines?

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    $\begingroup$ I just looked at the spectra in the reference. I do not think the interpretation of the spectra is credible. It's probably noise, and not einsteinium. $\endgroup$ Mar 6 at 2:12
  • $\begingroup$ I'll point out there is Astronomy if your main interest in astronomy related. $\endgroup$ Mar 6 at 14:16
  • $\begingroup$ @StephenG-HelpUkraine I am a part of Astronomy Stack as well, I just thought spectroscopy was slightly more physics than astronomy. You disagree? $\endgroup$
    – Jimmy G.
    Mar 6 at 19:26
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    $\begingroup$ Just a suggestion. Spectroscopy of stars and nucleosynthesis obviously brings astronomy and astrophysics to mind. It would be fine in either site I think. $\endgroup$ Mar 6 at 19:28
  • $\begingroup$ @StephenG-HelpUkraine I will ask my follow up there. Thank you for the help. $\endgroup$
    – Jimmy G.
    Mar 6 at 20:14

2 Answers 2

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We have previously discovered unknown elements spectroscopically. Helium (named for helios, “sun”) was identified in solar spectra decades before being isolated on Earth.

As for “how it is still there”: if you have short-lived isotopes whose populations are not decreasing over time, the decays must be in secular equilibrium with some production process. On Earth, we produce heavy actinides in chemically-significant quantities by repeated neutron capture on heavy elements.

There is speculation in nuclear physics that there may be an “island of stability” for very heavy nuclei. Or rather, speculation about a second “island of stability,” because there is already a gap between lead and uranium where all nuclides are short-lived. If such superheavy, relatively stable nuclei exist, and they are chemically important in this weird star, their decays could produce a population of nuclei which are too short-lived to occur in ores on Earth. There is precedent for this, too. The decay of trace amounts of uranium in concrete and bedrock can cause radon gas to accumulate in poorly-ventilated rooms.

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  • $\begingroup$ Would hydrogen be easier to detect than 119+, though? $\endgroup$
    – Jimmy G.
    Mar 6 at 21:03
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    $\begingroup$ Oh, the less of the stuff there is, the harder to see its spectrum. Helium was "low-hanging fruit" because it makes up almost a quarter of the Sun's mass. I share the skepticism expressed in your other answer about the identification of einsteinium, but I didn't comment because I haven't had a chance to read the paper. $\endgroup$
    – rob
    Mar 7 at 0:50
  • $\begingroup$ Stars only produce elements up to iron, right? So the production process for stable superheavy elements wouldn't be continuous; it would be something like a supernova. $\endgroup$ Mar 7 at 16:22
  • $\begingroup$ @TechInquisitor The s-process gets you as far as lead, continuously. As I understand it, the most likely source for actinides is merging neutron stars (kilonovae, see e.g.). The same would apply to hypothetical long-lived trans-actinides. Setting aside questions about exotica, some unknown process has enriched the atmosphere or this star with rare-earth elements. $\endgroup$
    – rob
    Mar 7 at 17:48
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I think that would be very difficult indeed. Unfortunately there are many elements, many isotopes and different ionisation states. Literally millions of transitions. Missing data and incorrectly estimated oscillator strengths mean there are often "unexplained" weak absorption lines in high resolution stellar spectra.

To make a convincing case for finding new elements there would have to be multiple lines identified and a reasonable calculation of where in the spectra those lines would be, based on some knowledge of the atomic physics for those elements. The lines themselves would have to be unblended from other nearby spectral lines and strong enough to be detected. This is not impossible, just very difficult.

I am not convinced by Gopka et al.'s identification of a single absorption line of Einsteinium. If it could be confirmed, then its short half-life means it was produced in the star. A leading explanation would be decay from heavier, long-lived elements in a hypothesised island of stability. Such elements themselves could be produced during neutron star mergers and the resultant kilonova explosions.

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  • $\begingroup$ I believe this answered another question I had about spectroscopy. So, you CAN differentiate between isotopes and ionization states? And, what about nuclear isomers? Imagining some star somewhere has large amounts of nuclear isomers, would you be able to differentiate those from the unexcited state? $\endgroup$
    – Jimmy G.
    Mar 6 at 19:32
  • $\begingroup$ Different ionisation states have completely different absorption spectra. Different isotopes have shifted wavelengths. @JimmyG. $\endgroup$
    – ProfRob
    Mar 6 at 19:36
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    $\begingroup$ I've quoted you in Chemistry SE How many elements have been identified for which there are no known spectral lines? Feel free to edit there further. $\endgroup$
    – uhoh
    Mar 7 at 0:11
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    $\begingroup$ @JimmyG. To get an idea for how hard lines are to identify, you can use the NIST atomic spectra database. Arbitrarily picking the band 500-501 nm gives dozens and dozens of lines, with atoms ranging from potassium to dysprosium. The I/II after the chemical symbol represents the ionisation state, I is neutral (spectroscopy has a lot of weird and annoying notation because it's such an old discipline) physics.nist.gov/PhysRefData/ASD/lines_form.html $\endgroup$
    – llama
    Mar 7 at 18:01
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    $\begingroup$ @llama Most rare heavy elements have their strongest transitions in the blue and UV where the crowding is even more intense ... $\endgroup$
    – ProfRob
    Mar 7 at 19:30

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