<p>Yes, we look into stellar spectra searching for whatever exotics. This way new elements were discovered (helium, in solar chromosphere), exotic states of other elements not studied well in terrestrial conditions (e.g. coronium, <a href="https://en.wikipedia.org/wiki/Coronium" rel="noreferrer">https://en.wikipedia.org/wiki/Coronium</a>).</p>
<p>Regarding positronium, it is short-lived, and is not accumulated in sufficient amounts to yield readily observable spectral features. The positronium decay <span class="math-container">$\gamma$</span>-quanta (511 keV line) <span class="math-container">$are$</span> observed (near the galactic center in particular; in pulsar spectra, etc.) Estimates for observing lines corresponding to transitions between different bound states of positronium are not very promising; e.g. <a href="https://ui.adsabs.harvard.edu/abs/1996A%26AS..120C.365B/abstract" rel="noreferrer">https://ui.adsabs.harvard.edu/abs/1996A%26AS..120C.365B/abstract</a></p>

CC BY-SA 4.0
2022-09-08T22:48:52.180Z
I've just asked a follow-up: [Can we see atomic positronium lines in space? What could be learned from it and what are current challenges to doing so?](https://astronomy.stackexchange.com/q/50405/7982)
uhoh
CC BY-SA 4.0
2022-09-08T16:54:23.790Z
2022-09-08T16:54:23.790Z
matteroffact
<p>I was reading this <a href="https://en.wikipedia.org/wiki/Positronium#:%7E:text=Positronium%20(Ps)%20is%20a%20system,on%20the%20relative%20spin%20states." rel="noreferrer">wikipedia article</a> on positronium (a type of exotic atom) and noticed it mentioned that positronium has a spectra (of course).</p>
<p>So naturally this makes me wonder, have we looked at stars or other glowing objects to try to detect spectra of exotic atoms? It seems plausible to me that there would be extremely faint but non-0 spectra of these exotic atoms within the stars, or maybe in the center of the galaxy.</p>

CC BY-SA 4.0
2022-09-03T02:05:41.560Z
*Cool question!* Potentially interesting in Chemistry SE is [this answer to *What is a "hydrogen-like" or "hydrogenic" atom?*](https://chemistry.stackexchange.com/a/80320/16035) One certainly sees annihilation photons from e+/e- pairs, certainly some come from decay of positronium, but I think that you are asking about electromagnetic transitions between bound states only (final state is still an exotic atom of some sort)?
uhoh
<observational-astronomy><spectroscopy><spectra><exotic-matter>
Have we detected spectra of exotic atoms in stars?
Sidharth Ghoshal
# Have we detected spectra of exotic atoms in stars?

(Asked by: username_0 on 2022-09-02)

I was reading this [wikipedia article](https://en.wikipedia.org/wiki/Positronium#:%7E:text=Positronium%20(Ps)%20is%20a%20system,on%20the%20relative%20spin%20states.) on positronium (a type of exotic atom) and noticed it mentioned that positronium has a spectra (of course).

So naturally this makes me wonder, have we looked at stars or other glowing objects to try to detect spectra of exotic atoms? It seems plausible to me that there would be extremely faint but non-0 spectra of these exotic atoms within the stars, or maybe in the center of the galaxy.

**Tags:** observational-astronomy, spectroscopy, spectra, exotic-matter

> **Comments:**
> **username_1**: *Cool question!* Potentially interesting in Chemistry SE is [this answer to *What is a "hydrogen-like" or "hydrogenic" atom?*](https://chemistry.stackexchange.com/a/80320/16035) One certainly sees annihilation photons from e+/e- pairs, certainly some come from decay of positronium, but I think that you are asking about electromagnetic transitions between bound states only (final state is still an exotic atom of some sort)?  

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## 1 answers

### Answer by username_2 on 2022-09-08. Score: 6 | Accepted answer

Yes, we look into stellar spectra searching for whatever exotics. This way new elements were discovered (helium, in solar chromosphere), exotic states of other elements not studied well in terrestrial conditions (e.g. coronium, <https://en.wikipedia.org/wiki/Coronium>).

Regarding positronium, it is short-lived, and is not accumulated in sufficient amounts to yield readily observable spectral features. The positronium decay $\gamma$-quanta (511 keV line) $are$ observed (near the galactic center in particular; in pulsar spectra, etc.) Estimates for observing lines corresponding to transitions between different bound states of positronium are not very promising; e.g. <https://ui.adsabs.harvard.edu/abs/1996A%26AS..120C.365B/abstract>

> **Comments:**
> **username_1**: I've just asked a follow-up: [Can we see atomic positronium lines in space? What could be learned from it and what are current challenges to doing so?](https://astronomy.stackexchange.com/q/50405/7982)  

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