
Przybylski's Star - sgt101
https://en.wikipedia.org/wiki/Przybylski%27s_Star
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tdy721
Yes Yes Yes! There's the distinction of "Natural Elements" and I've always
suspected that it was a somewhat temporal distinction. While I believe that
the Periodic Table is a Universal Truth, "Natural" vs "Man-Made" elements
always struck me as a Earthly way of looking at things. Not bad, just not the
whole truth.

~~~
jmiserez
Just FYI the periodic table also doesn't tell the full story. Take a look at
the isotope table:

[https://en.wikipedia.org/wiki/Table_of_nuclides_(complete)](https://en.wikipedia.org/wiki/Table_of_nuclides_\(complete\))

~~~
tdy721
I really love the Isotope Table. I seem to remember having a chemistry teacher
that mentioned something about the table being wonky or secretive. Total
hearsay.

I like the periodic table because I could verify it. Isotopes? Not so much...

~~~
jmiserez
I don't think there's anything wonky about that table, it's just often not in
the curriculum in high school, and teachers don't want to "confuse" students
with material outside of the curriculum. But for me it greatly simplified
understanding isotopes and radioactive decay.

And why would you think you couldn't verify it? All of the isotopes in the
table were observed in a lab somewhere.

~~~
darkfuji
"it's just often not in the curriculum in high school"

I'm pretty sure that most high school science students have at least seen it
before though.

~~~
ci5er
The Isotope Table? I'm old and rural, but I didn't come across it in high
school until I (an atypical geek) went looking for it specifically.

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urza
I dont understand, what significance does this star has? Why was it upvoded to
front page? What was the original title? Now it only says "Przybylski's Star"

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ojiikun
original title was "a star that has plutonium in its spectra"

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parenthephobia
The reason it's interesting is that the star appears to contain a variety of
short-lived isotopes, not just of plutonium: e.g. promethium-145, with a half-
life of just under 18 years.

Some as-yet unidentified process is replenishing the star's isotopes. An idea
I've seen[1] is that the radiation from its neutron star sibling, invisible to
us, is powerful enough to trigger nuclear reactions in the star's ionosphere.

1\. "A hypothesis for explaining the origin of Przybylski’s star (HD 101065)"
[http://link.springer.com/article/10.1007/s11963-008-1005-7](http://link.springer.com/article/10.1007/s11963-008-1005-7)

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givinguflac
Interesting. I wonder what elements are created when a rare star like this
goes supernova. Though as this type is so rare, we may not know if they even
do.

~~~
tdy721
The biggest baddest Particle Accelerators in the 'Verse. I'm fairly certain we
don't fully understand "common" supernovae.

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Stratoscope
A star can't have have plutonium in its spectra. A single star doesn't have
spectra, only a spectrum.

If you were talking about multiple stars, then yes, they would have spectra
(the plural of spectrum).

To be clear, I don't mean this as a criticism of the submitter. :-) In fact, I
appreciate that the title was changed from the original Wikipedia title to
bring out the interesting part. Just wanted to note a little detail of
spelling/grammar that is easily confused.

Plus, plutonium is only one of the interesting things about Przybylski's Star.
It is a really weird star!

~~~
wycx
I suspect we are confident that Pu is there because there are spectra
indicating its presence, as opposed to a single spectrum.

~~~
Stratoscope
Well, you may have me there. Now I am totally confused about whether it should
be spectrum or spectra.

I suppose that means it's time for me to call it a night!

~~~
wycx
I think of in terms of the data we collect. Make a single measurement over a
range of energies/wavelengths/frequencies and you have collected a spectrum.
Repeat that measurement or make measurements covering different
energies/wavelengths/frequencies and you have some spectra.

For the star from the article, I think it is fair to say that Pu consistently
appears in the spectra that have been collected.

~~~
Stratoscope
Thanks, that's an interesting way to look at it and makes complete sense to
me.

At the risk of sounding like a total nitpicker, I am still a bit confused. I
understand that you may measure the star's spectrum and get one result, and I
may measure it and get a different result, so now we have two different (but
hopefully fairly similar!) spectra for the star.

But does this mean that _the star itself_ now has two different spectra? Or is
it just that we've both measured it imperfectly and came out with different
results?

As another example, suppose we have an object with a mass of exactly one gram.
I measure it as 0.9999999 grams. You measure it as 1.0000001 grams.

Now we have two different masses for the object. Does that mean that the
object itself now has two different masses (plural)? Or does it still has a
single true mass of its own and we've both just suffered from experimental
error?

I hope anyone reading this is not too annoyed - I'm just trying to understand
how singular and plural work here, and to have some fun with the discussion.
:-)

~~~
thaumasiotes
> I'm just trying to understand how singular and plural work here, and to have
> some fun with the discussion.

Hey, that's my kind of discussion :)

There is no one "how singular and plural work here". Singular and plural
inflections are a tool speakers can use to express a dimension of their
thought; syntax isn't capable of fully determining which will appear.

Consider the sentence "my family are all Buddhists". "Family", the subject of
the sentence, is unambiguously a singular noun, with plural form "families".
The verb in the sentence is, also unambiguously, inflected for a plural
subject. It's inflected that way because the speaker wishes, for purposes of
the sentence, to conceive of their family as a collection of several people.
In another context, it would be unsurprising to see "family" with singular
verb agreement.

People may say "spectrum" or "spectra" based on what about the situation
they're describing they want to provide focus on.

~~~
Stratoscope
Many thanks to you as well as wycx, cperciva, and mirimir for engaging in the
conversation. I learned a few things from you all!

I must confess: after my initial comment started gathering downvotes I was on
the verge of deleting it. I'm glad I didn't, since it led to such an
interesting and informative discussion.

I've seen this fairly often on HN, where someone posts a comment that is
either factually wrong, off topic, or just something I strongly disagree with,
and then a very interesting conversation follows from that. I make a point of
upvoting the original comment along with the replies, since after all it was
that comment that sparked the discussion.

