<p>Not chemically peculiar. Local Group stars appear similar in composition. At least, to the extent that spectroscopy (“squiggly-line interpretation”) can nail down one star, let alone star-to-Sun differences.</p>
<p>The solar composition is measured as much (or more) from exceptional meteorites (CI chondrites) than spectroscopy:</p>
<p><a href="https://en.wikipedia.org/wiki/CI_chondrite" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/CI_chondrite</a></p>
<p>See also review article, <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/maps.13266" rel="nofollow noreferrer">The future of Genesis science, Meteoritics and Planetary Science</a>, 2019 May</p>
<p>Happy squiggling.</p>

CC BY-SA 4.0
2022-08-01T21:58:47.250Z
2022-08-02T00:41:09.830Z
2022-08-02T00:41:09.830Z
caInstrument
<p>No, the Sun is not &quot;chemically peculiar&quot;. (I'm not sure most astronomers would call HD 222925 chemically peculiar, either, certainly not in any of the ways discussed on the Wikipedia page.)</p>
<p>The video you link to is rather confused. What makes HD 222925 special is <em>not</em> that it is, overall, &quot;rich in elements&quot;. In fact, it is relatively metal-<em>poor</em>, with only about 3% of the Sun's iron abundance. The key things about it are: 1) the r-process elements are enhanced relative to other elements in that star; 2) it is relatively hot -- and thus produces significant UV light; and 3) it is -- because it is metal-poor -- lacking in iron-group elements. The latter fact means that the UV signatures of many r-process elements (including, yes, gold) are discernible in the UV spectrum in a way that would not be possible in a more metal-rich, hot star, where the UV spectrum is dominated by absorption lines from iron-group elements. (It is also bright enough to make high-signal-to-noise UV spectra possible.)</p>
<p>The Sun is relevant not because <em>it</em> is especially enhanced in r-process elements, but because we can know the abundances of all the r-process elements in the Solar System really well from analysis of <em>meteorites</em>. (The video's claim that the Solar System's r-process elements must have come from a single nearby neutron-star collision is erroneous, as is the attempt to suggest that r-process elements are important for life.)</p>

CC BY-SA 4.0
2022-07-31T23:02:47.527Z
2022-07-31T23:02:47.527Z
Peter Erwin
<p>In Wikipedia it defines <a href="https://en.wikipedia.org/wiki/Chemically_peculiar_star" rel="noreferrer">&quot;chemically peculiar stars (CP stars)&quot;</a> as,</p>
<blockquote>
<p>In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual metal abundances, at least in their surface layers.</p>
</blockquote>
<p><a href="https://en.wikipedia.org/wiki/HD_222925" rel="noreferrer">HD 222925</a> has been making a lot of news lately. In this video by Anton Petrov, <a href="https://youtu.be/_TE7LLWmcVE?t=115" rel="noreferrer"><em>&quot;Groundbreaking Image of the Most Element Rich Star Found to Date
&quot;</em></a> he says,</p>
<blockquote>
<p>[HD 222925] was always classified as &quot;chemically peculiar&quot; or basically unusual or somewhat strange and there is a really important reason for that. [...] With the exception of our own Sun this particular star seems to be extremely rich in various elements. A relatively recent study identified 65 various elements, chemical elements, including Gold with an overabundance of a lot of other metal that's never been seen before anywhere except in our own Sun.</p>
</blockquote>
<p>It sounds like HD 222925 is &quot;chemically peculiar&quot; <em>because</em> of the composition of the star. If so, is our Sun also &quot;chemically peculiar&quot;? And if not, what is the definition of &quot;chemically peculiar&quot; such that our Sun is <strong>NOT</strong> and HD 222925 is?</p>

CC BY-SA 4.0
2022-07-27T23:44:16.420Z
My *guess* is that we can get a lot more spectrographic data from sunlight than from starlight, simply due to the brightness.
PM 2Ring
CC BY-SA 4.0
2022-07-28T13:58:49.540Z
Interesting, but I think this is a matter of subjective, rather than objective, classification.
Carl Witthoft
CC BY-SA 4.0
2022-07-29T12:29:35.167Z
**I don't think this question should be closed and answer blocked** because it is "likely to be answered with opinions rather than facts and citations". The OP found something that sounds authoritative yet feels subjective, and has come here to Astronomy SE to clear this up. Instead of preventing anyone from posting an answer because the quoted bit from the link sounds subjective, let's *allow answers to be posted* so we can get to the bottom of this!
uhoh
CC BY-SA 4.0
2022-07-30T15:30:01.410Z
I agree with @uhoh  I previously upvoted this question because it is interesting and I was hoping to see a good answer. As well, the new echelle spectrograph at Gemini South targeted this particular star for its initial tests: “Gemini South telescope's GHOST spectrograph captures first light observations of a bright, chemically rich star
https://phys.org/news/2022-07-gemini-south-telescope-ghost-spectrograph.html.” So what gives with this star?
Ed V
CC BY-SA 4.0
2022-07-31T23:12:45.157Z
Very poor video.
ProfRob
<the-sun><elemental-abundances>
Is the Sun "chemically peculiar", and if not why is HD 222925?
Evan Carroll
# Is the Sun "chemically peculiar", and if not why is HD 222925?

(Asked by: username_0 on 2022-07-27)

In Wikipedia it defines ["chemically peculiar stars (CP stars)"](https://en.wikipedia.org/wiki/Chemically_peculiar_star) as,

> In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual metal abundances, at least in their surface layers.

[HD 222925](https://en.wikipedia.org/wiki/HD_222925) has been making a lot of news lately. In this video by Anton Petrov, [*"Groundbreaking Image of the Most Element Rich Star Found to Date
"*](https://youtu.be/_TE7LLWmcVE?t=115) he says,

> [HD 222925] was always classified as "chemically peculiar" or basically unusual or somewhat strange and there is a really important reason for that. [...] With the exception of our own Sun this particular star seems to be extremely rich in various elements. A relatively recent study identified 65 various elements, chemical elements, including Gold with an overabundance of a lot of other metal that's never been seen before anywhere except in our own Sun.

It sounds like HD 222925 is "chemically peculiar" *because* of the composition of the star. If so, is our Sun also "chemically peculiar"? And if not, what is the definition of "chemically peculiar" such that our Sun is **NOT** and HD 222925 is?

**Tags:** the-sun, elemental-abundances
> **Comments:**
> **username_1**: My *guess* is that we can get a lot more spectrographic data from sunlight than from starlight, simply due to the brightness.  
> **username_2**: Interesting, but I think this is a matter of subjective, rather than objective, classification.  
> **username_3**: **I don't think this question should be closed and answer blocked** because it is "likely to be answered with opinions rather than facts and citations". The OP found something that sounds authoritative yet feels subjective, and has come here to Astronomy SE to clear this up. Instead of preventing anyone from posting an answer because the quoted bit from the link sounds subjective, let's *allow answers to be posted* so we can get to the bottom of this!  
> **username_4**: I agree with @uhoh  I previously upvoted this question because it is interesting and I was hoping to see a good answer. As well, the new echelle spectrograph at Gemini South targeted this particular star for its initial tests: “Gemini South telescope's GHOST spectrograph captures first light observations of a bright, chemically rich star https://phys.org/news/2022-07-gemini-south-telescope-ghost-spectrograph.html.” So what gives with this star?  
> **username_5**: Very poor video.  

---

## 2 answers

### Answer by username_7 on 2022-07-31. Score: 10 | Accepted answer

No, the Sun is not "chemically peculiar". (I'm not sure most astronomers would call HD 222925 chemically peculiar, either, certainly not in any of the ways discussed on the Wikipedia page.)

The video you link to is rather confused. What makes HD 222925 special is *not* that it is, overall, "rich in elements". In fact, it is relatively metal-*poor*, with only about 3% of the Sun's iron abundance. The key things about it are: 1) the r-process elements are enhanced relative to other elements in that star; 2) it is relatively hot -- and thus produces significant UV light; and 3) it is -- because it is metal-poor -- lacking in iron-group elements. The latter fact means that the UV signatures of many r-process elements (including, yes, gold) are discernible in the UV spectrum in a way that would not be possible in a more metal-rich, hot star, where the UV spectrum is dominated by absorption lines from iron-group elements. (It is also bright enough to make high-signal-to-noise UV spectra possible.)

The Sun is relevant not because *it* is especially enhanced in r-process elements, but because we can know the abundances of all the r-process elements in the Solar System really well from analysis of *meteorites*. (The video's claim that the Solar System's r-process elements must have come from a single nearby neutron-star collision is erroneous, as is the attempt to suggest that r-process elements are important for life.)


---

### Answer by username_6 on 2022-08-01. Score: 1

Not chemically peculiar. Local Group stars appear similar in composition. At least, to the extent that spectroscopy (“squiggly-line interpretation”) can nail down one star, let alone star-to-Sun differences.

The solar composition is measured as much (or more) from exceptional meteorites (CI chondrites) than spectroscopy:

<https://en.wikipedia.org/wiki/CI_chondrite>

See also review article, [The future of Genesis science, Meteoritics and Planetary Science](https://onlinelibrary.wiley.com/doi/full/10.1111/maps.13266), 2019 May

Happy squiggling.


---

