<p>This question is about celestrial objects which are composed by exotic matter, and <a href="https://en.wikipedia.org/wiki/Exotic_matter" rel="nofollow noreferrer">exotic matter</a> I define as</p>
<blockquote>
<p><strong>states of matter that are not commonly encountered</strong> such as Bose–Einstein condensates, fermionic condensates, nuclear matter, quantum spin liquid, string-net liquid, supercritical fluid, color-glass condensate, quark–gluon plasma, [...] but <strong>whose properties are entirely within the realm of mainstream physics.</strong> [Bold text from me.]</p>
</blockquote>
<p>The most obvious candidate is a neutron star (see <a href="/questions/tagged/neutron-star" class="post-tag" title="show questions tagged &#39;neutron-star&#39;" rel="tag">neutron-star</a>), but I also heard about hypothetical <a href="https://en.wikipedia.org/wiki/Exotic_star" rel="nofollow noreferrer">exotic stars</a> like the <a href="https://en.wikipedia.org/wiki/Quark_star" rel="nofollow noreferrer">Quark star</a>, but I am unsure how hypothetical those are. <strong>I am after exotic matter objects which could (at least theoretically) be somehow observed.</strong></p>
<p>I stumbled upon the Space.com article <em><a href="https://www.space.com/alien-planets-pulsars-strange-matter.html" rel="nofollow noreferrer">These 'Strange' Alien Planets May Be Made of Exotic Matter</a></em>:</p>
<blockquote>
<p>However, previous research also indicated that planets made of strange matter could exist and  that scientists might distinguish these planets from planets made of conventional matter via their densities. Normal planets have densities that are no more than 1,870 lbs. per cubic foot (30 grams per cubic centimeter). In contrast, strange planets would typically have densities of nearly 25 million billion lbs. per cubic foot (400 trillion grams per cubic centimeter), Geng and his colleagues said. (For comparison, gold has a density of about 1,200 lbs. per cubic foot, or nearly 19.3 grams per cubic centimeter.)</p>
</blockquote>
<p>This adds strange matter exoplanets to my list of exotic matter astronomical objects, isn't it? Are there other exotic matter objects I am missing?</p>

CC BY-SA 4.0
2021-03-09T16:05:02.977Z
I think a red dwarf old enough to have fused its hydrogen reserves to helium, and then cooled enough to become superfluid would qualify. But as they stay in main sequence for trillions of years, probably none reached this state yet.
ksousa
CC BY-SA 4.0
2021-03-09T18:17:32.090Z
More of a red dwarf remnant.
ksousa
CC BY-SA 4.0
2021-03-09T21:21:43.943Z
White dwarfs are a little exotic too, but maybe not exotic enough?
Kristoffer Sjöö
CC BY-SA 4.0
2021-03-09T22:24:14.677Z
@KristofferSjöö White dwarves are indeed exotic enough, I forgot to mention them in my question. Thanks.
B--rian
<observational-astronomy><exoplanet><neutron-star><exotic-matter>
Strange matter objects other than neutron stars?
B--rian
# Strange matter objects other than neutron stars?

(Asked by: username_0 on 2021-03-09)

This question is about celestrial objects which are composed by exotic matter, and [exotic matter](https://en.wikipedia.org/wiki/Exotic_matter) I define as

> **states of matter that are not commonly encountered** such as Bose–Einstein condensates, fermionic condensates, nuclear matter, quantum spin liquid, string-net liquid, supercritical fluid, color-glass condensate, quark–gluon plasma, [...] but **whose properties are entirely within the realm of mainstream physics.** [Bold text from me.]

The most obvious candidate is a neutron star (see [neutron-star](/questions/tagged/neutron-star "show questions tagged 'neutron-star'")), but I also heard about hypothetical [exotic stars](https://en.wikipedia.org/wiki/Exotic_star) like the [Quark star](https://en.wikipedia.org/wiki/Quark_star), but I am unsure how hypothetical those are. **I am after exotic matter objects which could (at least theoretically) be somehow observed.**

I stumbled upon the Space.com article *[These 'Strange' Alien Planets May Be Made of Exotic Matter](https://www.space.com/alien-planets-pulsars-strange-matter.html)*:

> However, previous research also indicated that planets made of strange matter could exist and that scientists might distinguish these planets from planets made of conventional matter via their densities. Normal planets have densities that are no more than 1,870 lbs. per cubic foot (30 grams per cubic centimeter). In contrast, strange planets would typically have densities of nearly 25 million billion lbs. per cubic foot (400 trillion grams per cubic centimeter), Geng and his colleagues said. (For comparison, gold has a density of about 1,200 lbs. per cubic foot, or nearly 19.3 grams per cubic centimeter.)

This adds strange matter exoplanets to my list of exotic matter astronomical objects, isn't it? Are there other exotic matter objects I am missing?

**Tags:** observational-astronomy, exoplanet, neutron-star, exotic-matter
> **Comments:**
> **username_1**: I think a red dwarf old enough to have fused its hydrogen reserves to helium, and then cooled enough to become superfluid would qualify. But as they stay in main sequence for trillions of years, probably none reached this state yet.  
> **username_1**: More of a red dwarf remnant.  
> **username_2**: White dwarfs are a little exotic too, but maybe not exotic enough?  
> **username_0**: @KristofferSjöö White dwarves are indeed exotic enough, I forgot to mention them in my question. Thanks.  

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## 0 answers

