<p>Your question misunderstands what is being claimed when someone says that a &quot;stellar-mass black hole&quot; (candidate) is actually a quark star.</p>
<p>The two things are entirely different and the existence of one type of object does not preclude the existence of, or have any bearing on the nature of, the other.</p>
<p>Stellar mass black hole (candidates) are generally objects with mass greater than around 3 solar masses that are established (by some means) to be extremely compact or are undetectably faint so that they cannot be &quot;normal&quot; stars.</p>
<p>Their high mass usually precludes them from being stable neutron stars (or any other type of compact object). That is because most reasonable equations of state, combined with General Relativity, do not permit a stable star of such mass to exist.</p>
<p>The paper you cite is pay-walled. The abstract claims that stellar mass black hole candidates between 3 and 8 solar masses may in fact be rapidly rotating &quot;quark stars&quot;. I surmise from this abstract that the authors are claiming that it <em>is</em> possible to construct a stable compact star at these masses, providing it is rapidly rotating and made of quark matter.</p>
<p>If they are quark stars, then they are not black holes.</p>
<p>Whether this bears scrutiny as a theoretical idea I do not know (the paper is just from a conference proceedings and has not been refereed), but whether it is true or not is irrelevant to considering the nature of black holes, which by definition, cannot be stable compact stars. Indeed, the same abstract suggests observational tests to distinguish between the two possibilities.</p>
<p>The nature of the infinities that occur at the physical singularities associated with General Relativistic black holes are widely discussed and it is widely accepted that they are likely to be a consequence of an incomplete understanding of what happens to matter crushed into extremely high densities. However, a defining characteristic of a black hole is it has an event horizon; whatever this physics is would appear to happen in a region of spacetime that cannot be observed and so would not affect the observable properties and consequences of black holes.</p>

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2024-10-22T16:55:29.853Z
Thank you for that point of clarity, I think I can now see the subtlety in distinguishing "candidates" from black holes themselves. You're saying that if quark stars exist, we might be confusing them for small enough black holes, since quark stars aren't a conventionally proven object, is that correct?
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ProfRob
<p>Recent data and theorization suggests the possibility that stellar-mass black holes may actually be quark stars: <a href="https://ui.adsabs.harvard.edu/abs/2012mgm..conf..943H/abstract" rel="nofollow noreferrer">https://ui.adsabs.harvard.edu/abs/2012mgm..conf..943H/abstract</a></p>
<p>where infalling matter would get crushed into the interior quark star's surface, maybe.</p>
<p>Does that mean the interior of black holes can be quark stars?</p>
<p><strong>IMPORTANT NOTE:</strong> *If it's impossible, please suggest evidence on why you think that is the case, rather than resorting to demagoguery.</p>

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@RoryAlsop For instance, can gravity be considered a fictitious force? Well, I'm not a physicist, but a physicist did tell me that. But you've provided no helpful information on whether that interpretation is true or false, you're just ranting at me, a non-physicist, non-astronomer, who is asking a question on a site that ***literally exists *** for asking questions.
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@RoryAlsop Okay, if it's reasonable to assume infinite dilation and infinite length contraction exists, can you point me to experimental proving as such? You're making claims that the conclusion isn't reasonable, but you're not providing any reason why, you're just saying almost random colloquial sentences that have nothing to do with science, whereas I'm engaged in reading science. If you're such an avid reader, why don't you point me to a contemporary article proving space-time isn't quantized?
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@RoryAlsop "Bad" is completely subjective, but I am on topic and asking an astronomy related question that had thought and formulation and reading before hand, and you have also, hypocritically, not provided scientific evidence for your claims of the truth or falsehood of the original post. Just ask yourself this: if I don't "read" research, how in the hell did I find that article and then read it enough to try asking a question about it? You're not even putting effort into helping me and other layman who have similar questions, you're here to be elitist and rant at non-physics-graduates.
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I have told you in the chat and multiple times - like others, the aim is to help you improve your question to meet site requirements so it can provide value to future visitors. You deciding to take things personally, and get abusive is not going to help you in any way. I'm not going to try and help you any more. Good luck.
Rory Alsop
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@RoryAlsop Thank you for finally not talking to me. You don't see me going to other people's questions and trying to police them, arbitrarily, or downvote them either. Nothing you've provided has helped me ask better questions. If anything, you've made it worse, because now I have even less inclination to put time into questions after you wasted that time arguing with me.
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@RoryAlsop The aim of *other people*, some times, rarely, on occasion, is to "help" improve questions. That is not your aim. I can tell that's not your aim because I'm a lot more angry at stackexchange because of you, and because I have years of experience tutoring science and math, and nothing I see from you is what I would impose on any students. You used offensive deragotry language directed at me and my questions. Then, instead of admitting you were mistaken to blatantly offend me, you argued with me, making my experience on this site even worse.
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<observational-astronomy><black-hole><neutron-star>
Can black holes actually be quark stars?
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# Can black holes actually be quark stars?

(Asked by: username_0 on 2024-10-22)

Recent data and theorization suggests the possibility that stellar-mass black holes may actually be quark stars: <https://ui.adsabs.harvard.edu/abs/2012mgm..conf..943H/abstract>

where infalling matter would get crushed into the interior quark star's surface, maybe.

Does that mean the interior of black holes can be quark stars?

**IMPORTANT NOTE:** \*If it's impossible, please suggest evidence on why you think that is the case, rather than resorting to demagoguery.

**Tags:** observational-astronomy, black-hole, neutron-star
> **Comments:**
> **username_0**: @RoryAlsop For instance, can gravity be considered a fictitious force? Well, I'm not a physicist, but a physicist did tell me that. But you've provided no helpful information on whether that interpretation is true or false, you're just ranting at me, a non-physicist, non-astronomer, who is asking a question on a site that ***literally exists *** for asking questions.  
> **username_0**: @RoryAlsop Okay, if it's reasonable to assume infinite dilation and infinite length contraction exists, can you point me to experimental proving as such? You're making claims that the conclusion isn't reasonable, but you're not providing any reason why, you're just saying almost random colloquial sentences that have nothing to do with science, whereas I'm engaged in reading science. If you're such an avid reader, why don't you point me to a contemporary article proving space-time isn't quantized?  
> **username_0**: @RoryAlsop "Bad" is completely subjective, but I am on topic and asking an astronomy related question that had thought and formulation and reading before hand, and you have also, hypocritically, not provided scientific evidence for your claims of the truth or falsehood of the original post. Just ask yourself this: if I don't "read" research, how in the hell did I find that article and then read it enough to try asking a question about it? You're not even putting effort into helping me and other layman who have similar questions, you're here to be elitist and rant at non-physics-graduates.  
> **username_1**: I have told you in the chat and multiple times - like others, the aim is to help you improve your question to meet site requirements so it can provide value to future visitors. You deciding to take things personally, and get abusive is not going to help you in any way. I'm not going to try and help you any more. Good luck.  
> **username_0**: @RoryAlsop Thank you for finally not talking to me. You don't see me going to other people's questions and trying to police them, arbitrarily, or downvote them either. Nothing you've provided has helped me ask better questions. If anything, you've made it worse, because now I have even less inclination to put time into questions after you wasted that time arguing with me.  
> **username_0**: @RoryAlsop The aim of *other people*, some times, rarely, on occasion, is to "help" improve questions. That is not your aim. I can tell that's not your aim because I'm a lot more angry at stackexchange because of you, and because I have years of experience tutoring science and math, and nothing I see from you is what I would impose on any students. You used offensive deragotry language directed at me and my questions. Then, instead of admitting you were mistaken to blatantly offend me, you argued with me, making my experience on this site even worse.  

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## 1 answers

### Answer by username_2 on 2024-10-22. Score: 5 | Accepted answer

Your question misunderstands what is being claimed when someone says that a "stellar-mass black hole" (candidate) is actually a quark star.

The two things are entirely different and the existence of one type of object does not preclude the existence of, or have any bearing on the nature of, the other.

Stellar mass black hole (candidates) are generally objects with mass greater than around 3 solar masses that are established (by some means) to be extremely compact or are undetectably faint so that they cannot be "normal" stars.

Their high mass usually precludes them from being stable neutron stars (or any other type of compact object). That is because most reasonable equations of state, combined with General Relativity, do not permit a stable star of such mass to exist.

The paper you cite is pay-walled. The abstract claims that stellar mass black hole candidates between 3 and 8 solar masses may in fact be rapidly rotating "quark stars". I surmise from this abstract that the authors are claiming that it *is* possible to construct a stable compact star at these masses, providing it is rapidly rotating and made of quark matter.

If they are quark stars, then they are not black holes.

Whether this bears scrutiny as a theoretical idea I do not know (the paper is just from a conference proceedings and has not been refereed), but whether it is true or not is irrelevant to considering the nature of black holes, which by definition, cannot be stable compact stars. Indeed, the same abstract suggests observational tests to distinguish between the two possibilities.

The nature of the infinities that occur at the physical singularities associated with General Relativistic black holes are widely discussed and it is widely accepted that they are likely to be a consequence of an incomplete understanding of what happens to matter crushed into extremely high densities. However, a defining characteristic of a black hole is it has an event horizon; whatever this physics is would appear to happen in a region of spacetime that cannot be observed and so would not affect the observable properties and consequences of black holes.

> **Comments:**
> **username_0**: Thank you for that point of clarity, I think I can now see the subtlety in distinguishing "candidates" from black holes themselves. You're saying that if quark stars exist, we might be confusing them for small enough black holes, since quark stars aren't a conventionally proven object, is that correct?  

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