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Supermassive Dark Star candidates seen by JWST

218 points by misja111 3y ago

andsoitis 3y ago
> The first phase of stellar evolution in the history of the universe may be Dark Stars (DS), powered by dark matter (DM) heating rather than by nuclear fusion. Is "heating" the right way to think about the power from dark matter? Isn't "heating" a function of regular energy and matter?
- misja111 3y ago
  > Dark Stars, which are made almost entirely of hydrogen and helium with less than 0.1% of the mass in the form of DM. So most of the dark star is still ordinary matter, DM just adds a bit of extra gravity.
  - holmium 3y ago
    But, it's the DM that would provide the heat/glow for the star: > If the DM particles are their own antiparticles, then their annihilation provides a heat source that stops the collapse of the clouds and in fact produces a different type of star, a Dark Star, in thermal and hydrostatic equilibrium. > Three key ingredients are required for the formation of DSs: > 1) sufficient DM density > 2) DM annihilation products become trapped inside the star > 3) the DM heating rate beats the cooling rate of the collapsing cloud.
    - orra 3y ago
      > If the DM particles are their own antiparticles, then their annihilation provides a heat source How much if this is speculation? Also, do other particles behave like this? I didn't realise particles could be their own antiparticles, but it transpires that e.g. photons are, because all photons are neutral, not charged somehow. However, even though a proton is its own antiparticles, two photons do not annihilate, right?
      - ben_w 3y ago
        > Also, do other particles behave like this? Yes, as you note, photons are their own antiparticles. The maths doesn't have a preferred time direction, so two photons can annihilate into an electron-positron pair. I'm not sure if this has actually been observed given how hard it is. That said, my favourite type of supernova is caused by pair creation, though I don't know the proportion of that which comes from 2-photon interactions: https://en.wikipedia.org/wiki/Pair-instability_supernova https://en.wikipedia.org/wiki/Pair-instability_supernova There's also Majorna particles, but as I understand it the only known particles that are definitely Majornas are also quasiparticles: https://en.wikipedia.org/wiki/Majorana_fermion https://en.wikipedia.org/wiki/Majorana_fermion
        kamilner 3y ago
        Notably it does bound the energy of gamma rays over long distances (as the higher the energy the more likely it will annihilate with other photons along the way.) The wikipedia article on the Breit-Wheeler process has some history of the work on experimental observations, although I don't know how accurate or up to date it is https://en.wikipedia.org/wiki/Breit–Wheeler_process https://en.wikipedia.org/wiki/Breit–Wheeler_process
        AnimalMuppet 3y ago
        > The maths doesn't have a preferred time direction, so two photons can annihilate into an electron-positron pair. But only if their energy is high enough. So by that reckoning, photons below 511 keV don't have antiparticles, and those above it do. That's pretty weird. So maybe it's better to say that photons aren't really their own antiparticle, but they might theoretically destroy each other in some rare circumstances.
      - deleted 3y ago
        [deleted]
      - gus_massa 3y ago
        > Also, do other particles behave like this? Nobody is sure, but some people think that neutrinos are they own antiparticle https://en.wikipedia.org/wiki/Neutrino#Majorana_mass https://en.wikipedia.org/wiki/Neutrino#Majorana_mass I never liked that theory, but some people that know more than me about particle physics liked it. There were some experiment using atoms that decay ejecting two neutrinos, and hopping that in some case the two neutrinos will annihilate each other. https://en.wikipedia.org/wiki/Neutrinoless_double_beta_decay https://en.wikipedia.org/wiki/Neutrinoless_double_beta_decay . IIRC, none of the experiments found the strange annihilation, so perhaps neutrinos are not their own antiparticle :) .
- jessriedel 3y ago
  Heat is an abstract thermodynamic concept that does not depend on the particle species. For instance, the leading class of theory of dark matter is called "cold dark matter", and this literally refers to the temperature of the dark matter.
  - floxy 3y ago
    >The different theories on dark matter (cold, warm, hot) refer not to the temperatures of the matter itself, but the size of the particles themselves with respect to the size of a protogalaxy https://phys.org/news/2016-08-dark-matterhot.html https://phys.org/news/2016-08-dark-matterhot.html
    - jessriedel 3y ago
      That article is wrong. (More generally, phys.org cannot be trusted.) The cold/warm/hot absolutely refers to temperature, specifically whether the typical thermal speed is much less than (cold) or comparable to (hot) the speed of light. https://en.wikipedia.org/wiki/Cold_dark_matter https://en.wikipedia.org/wiki/Cold_dark_matter https://www.symmetrymagazine.org/article/is-dark-matter-cold-warm-or-hot https://www.symmetrymagazine.org/article/is-dark-matter-cold...
      - floxy 3y ago
        Thermal speed depends on the mass of the particle at a given temperature, correct? Like a volume of hydrogen has a much higher thermal speed than the same volume of radon at the same temperature. https://en.wikipedia.org/wiki/Thermal_velocity https://en.wikipedia.org/wiki/Thermal_velocity The article from Symmetry Magazine says the same thing as the Phys.org article: >Light, fast particles are known as hot dark matter; heavy, slow ones are cold dark matter; and warm dark matter falls in between. The dark matter in the early universe would have been at the same temperature whether of the "warm" or "cold" type, it is just that the speed of the "warm"/non-heavy types would have been too fast to have caused the clumping we see. Or at least that's how I understood it. But that Symmetry article is a good one as well.
- bowsamic 3y ago
  > Isn't "heating" a function of regular energy and matter? I'm a bit confused at what made you think this. If there is any way to transfer energy from it to something else (which there must be, else it would be impossible to ever interact with it), then it can heat in exactly the same way as anything else.
  - andsoitis 3y ago
    Thanks. That makes sense. I think the confusing thing for me is that dark matter doesn’t interact with the electromagnetic field so it doesn’t reflect, absorb, or emit electromagnetic radiation. But your explanation makes sense to me.
    - Sharlin 3y ago
      As the article says, the proposed mechanism is self-annihilation, which would presumably produce energy in the form of perfectly ordinary photons.
      - AnimalMuppet 3y ago
        That seems wrong. "Dark matter" usually means matter that doesn't interact with photons, not just "matter that is dark because no light is shining on it". But if it emits photons, even in a matter-antimatter reaction, then it couples with photons, and so it can't be dark matter in that sense.
        Sharlin 3y ago
        Apparently (eg. [1]) there would be a couple of different pathways available for WIMP annihilation, to a W⁺W⁻ boson pair, or to μ⁺μ⁻ muon pair, or a e⁺e⁻ electron-positron pair, so the immediate annihilation products would be charged non-dark matter particles which would either quickly decay or annihilate into photons or simply shed their energy via normal EM interactions. [1] P. Salati, 2014. Dark Matter Annihilation in the Universe. https://arxiv.org/abs/1403.4495 https://arxiv.org/abs/1403.4495
        3y ago
- Quinner 3y ago
  The authors are supposing that dark matter at this stage of the universe has its own particles and antiparticles and they are annihilating each other, the energy released by that annihilation is generating the heat.
  - denton-scratch 3y ago
    Thanks, I wondered where this notion of "DM heating" came from, and why the DM "ran out". But if the DM runs out, then you'd expect the same to happen for non-DM matter, which it doesn't.
    - jeremyjh 3y ago
      Anti-matter is very rare with normal matter, so we don’t see it running out. But if dark matter and dark anti-matter are both just as common then you could see it play out as they suggest.
      - pfdietz 3y ago
        Some models of dark matter have the particles being their own antiparticles.
        JumpCrisscross 3y ago
        Is it just charge that causes particles to have an antiparticle?
        pfdietz 3y ago
        No. Neutrons and antineutrons are different particles, for example.
        lanna 3y ago
        Neutrons don't have charge, but their quarks do. Antineutrons have quarks with reversed charge. Just like a neutral atom can have a neutral antiatom.
gnatman 3y ago
[flagged]
Pxtl 3y ago
I'm surprised to read an article with so much assumed knowledge about dark matter - about how it heats, etc. Is there a good place to read about the current best-guesses of the properties of dark matter?
- dylan604 3y ago
  Isn't the concept of dark matter just an assumption in itself? Seems to follow that any knowledge about it would be an assumption. In fact, that seems like good science, on instead of the word assumption, one might use theory. Once the theory is built up to test, it might actually one day become fact (or proven wrong).
  - phkahler 3y ago
    The word they should be using is hypothesis, not theory. A theory stands up to scrutiny.
    - dylan604 3y ago
      there you go, an even better word. good thing i don't call myself a scientist
    - mr_mitm 3y ago
      That's not how the term "theory" is used in science. Only hobbyists care about the distinction, actual scientists infer the implied certainty from context. There is Born's rule, Noether's theorem, Newton's law (which we know is wrong), Einstein's theory of GR, the standard model (which is the best thing we have), ... sometimes we use the word "a quantum theory" to mean a certain Lagrangian, even one which we know does not describe reality at all.
      - consilient 3y ago
        > Noether's theorem is not like the other entries on your list. It's a full-blown mathematically rigorous theorem (that incidentally also happens to be of central importance in physics), not a physical model.
ajross 3y ago
Seems like a reasonably professional paper by real authors, but the abstract seems suspiciously handwavy while the content is a bit thick for me. Can we get a BS check from the physicists here? Is this a good area for inquiry or just mining a giant data set for confirmation of a wonky idea? Also: what's the "heating" mechanism proposed? Dark matter infall would pick up energy I guess, but if it's expected to interact only with gravity that doesn't seem likely to do anything meaningful vs. the same cloud contracting on its own? What's being heated?
- samus 3y ago
  There are two possible mechanisms referred to in the article: weakly interacting particles (WIMPs) or self-annihilating dark matter.
deleted 3y ago
[deleted]
fhars 3y ago
I sort of like the idea of a "dark star" shining "with up to ten billion solar luminosities"...
bongwater_OS 3y ago
They didn't need to use JWST to find a transcendental Dark Star, they could have just looked at Fillmore West in 1969.
jbotz 3y ago
So, IIUC, this is an alternative to the paper that was discussed a couple of days ago saying the Universe might be twice as old as previously thought. The "problem observations" both of them try to address are what appear to be huge galaxies at an early time (according to redshift) when there shouldn't have been such large galaxies yet. The aforementioned paper says maybe the Universe is actually much older. This paper says maybe those huge early galaxies aren't actually galaxies but "Dark Stars" instead.
neuralengine 3y ago
Not attempting to claim malfeasance or anything but PNAS has a weird "contributed article" track (this article is one of them) in which the authors _can pick their own reviewers_ [1]. "Only 18% of direct submissions were published in 2013, whereas more than 98% of contributed papers were published, according to figures on the journal's website" [2]. [1] https://www.pnas.org/author-center/member-contributed-submissions https://www.pnas.org/author-center/member-contributed-submis... [2] https://www.nature.com/articles/510330a https://www.nature.com/articles/510330a

218 points by misja111 3y ago

> The first phase of stellar evolution in the history of the universe may be Dark Stars (DS), powered by dark matter (DM) heating rather than by nuclear fusion. Is "heating" the right way to think about the power from dark matter? Isn't "heating" a function of regular energy and matter?

misja111 3y ago
> Dark Stars, which are made almost entirely of hydrogen and helium with less than 0.1% of the mass in the form of DM. So most of the dark star is still ordinary matter, DM just adds a bit of extra gravity.
- holmium 3y ago
  But, it's the DM that would provide the heat/glow for the star: > If the DM particles are their own antiparticles, then their annihilation provides a heat source that stops the collapse of the clouds and in fact produces a different type of star, a Dark Star, in thermal and hydrostatic equilibrium. > Three key ingredients are required for the formation of DSs: > 1) sufficient DM density > 2) DM annihilation products become trapped inside the star > 3) the DM heating rate beats the cooling rate of the collapsing cloud.
  - orra 3y ago
    > If the DM particles are their own antiparticles, then their annihilation provides a heat source How much if this is speculation? Also, do other particles behave like this? I didn't realise particles could be their own antiparticles, but it transpires that e.g. photons are, because all photons are neutral, not charged somehow. However, even though a proton is its own antiparticles, two photons do not annihilate, right?
    - ben_w 3y ago
      > Also, do other particles behave like this? Yes, as you note, photons are their own antiparticles. The maths doesn't have a preferred time direction, so two photons can annihilate into an electron-positron pair. I'm not sure if this has actually been observed given how hard it is. That said, my favourite type of supernova is caused by pair creation, though I don't know the proportion of that which comes from 2-photon interactions: https://en.wikipedia.org/wiki/Pair-instability_supernova https://en.wikipedia.org/wiki/Pair-instability_supernova There's also Majorna particles, but as I understand it the only known particles that are definitely Majornas are also quasiparticles: https://en.wikipedia.org/wiki/Majorana_fermion https://en.wikipedia.org/wiki/Majorana_fermion
      - kamilner 3y ago
        Notably it does bound the energy of gamma rays over long distances (as the higher the energy the more likely it will annihilate with other photons along the way.) The wikipedia article on the Breit-Wheeler process has some history of the work on experimental observations, although I don't know how accurate or up to date it is https://en.wikipedia.org/wiki/Breit–Wheeler_process https://en.wikipedia.org/wiki/Breit–Wheeler_process
      - AnimalMuppet 3y ago
        > The maths doesn't have a preferred time direction, so two photons can annihilate into an electron-positron pair. But only if their energy is high enough. So by that reckoning, photons below 511 keV don't have antiparticles, and those above it do. That's pretty weird. So maybe it's better to say that photons aren't really their own antiparticle, but they might theoretically destroy each other in some rare circumstances.
    - deleted 3y ago
      [deleted]
    - gus_massa 3y ago
      > Also, do other particles behave like this? Nobody is sure, but some people think that neutrinos are they own antiparticle https://en.wikipedia.org/wiki/Neutrino#Majorana_mass https://en.wikipedia.org/wiki/Neutrino#Majorana_mass I never liked that theory, but some people that know more than me about particle physics liked it. There were some experiment using atoms that decay ejecting two neutrinos, and hopping that in some case the two neutrinos will annihilate each other. https://en.wikipedia.org/wiki/Neutrinoless_double_beta_decay https://en.wikipedia.org/wiki/Neutrinoless_double_beta_decay . IIRC, none of the experiments found the strange annihilation, so perhaps neutrinos are not their own antiparticle :) .
jessriedel 3y ago
Heat is an abstract thermodynamic concept that does not depend on the particle species. For instance, the leading class of theory of dark matter is called "cold dark matter", and this literally refers to the temperature of the dark matter.
- floxy 3y ago
  >The different theories on dark matter (cold, warm, hot) refer not to the temperatures of the matter itself, but the size of the particles themselves with respect to the size of a protogalaxy https://phys.org/news/2016-08-dark-matterhot.html https://phys.org/news/2016-08-dark-matterhot.html
  - jessriedel 3y ago
    That article is wrong. (More generally, phys.org cannot be trusted.) The cold/warm/hot absolutely refers to temperature, specifically whether the typical thermal speed is much less than (cold) or comparable to (hot) the speed of light. https://en.wikipedia.org/wiki/Cold_dark_matter https://en.wikipedia.org/wiki/Cold_dark_matter https://www.symmetrymagazine.org/article/is-dark-matter-cold-warm-or-hot https://www.symmetrymagazine.org/article/is-dark-matter-cold...
    - floxy 3y ago
      Thermal speed depends on the mass of the particle at a given temperature, correct? Like a volume of hydrogen has a much higher thermal speed than the same volume of radon at the same temperature. https://en.wikipedia.org/wiki/Thermal_velocity https://en.wikipedia.org/wiki/Thermal_velocity The article from Symmetry Magazine says the same thing as the Phys.org article: >Light, fast particles are known as hot dark matter; heavy, slow ones are cold dark matter; and warm dark matter falls in between. The dark matter in the early universe would have been at the same temperature whether of the "warm" or "cold" type, it is just that the speed of the "warm"/non-heavy types would have been too fast to have caused the clumping we see. Or at least that's how I understood it. But that Symmetry article is a good one as well.
bowsamic 3y ago
> Isn't "heating" a function of regular energy and matter? I'm a bit confused at what made you think this. If there is any way to transfer energy from it to something else (which there must be, else it would be impossible to ever interact with it), then it can heat in exactly the same way as anything else.
- andsoitis 3y ago
  Thanks. That makes sense. I think the confusing thing for me is that dark matter doesn’t interact with the electromagnetic field so it doesn’t reflect, absorb, or emit electromagnetic radiation. But your explanation makes sense to me.
  - Sharlin 3y ago
    As the article says, the proposed mechanism is self-annihilation, which would presumably produce energy in the form of perfectly ordinary photons.
    - AnimalMuppet 3y ago
      That seems wrong. "Dark matter" usually means matter that doesn't interact with photons, not just "matter that is dark because no light is shining on it". But if it emits photons, even in a matter-antimatter reaction, then it couples with photons, and so it can't be dark matter in that sense.
      - Sharlin 3y ago
        Apparently (eg. [1]) there would be a couple of different pathways available for WIMP annihilation, to a W⁺W⁻ boson pair, or to μ⁺μ⁻ muon pair, or a e⁺e⁻ electron-positron pair, so the immediate annihilation products would be charged non-dark matter particles which would either quickly decay or annihilate into photons or simply shed their energy via normal EM interactions. [1] P. Salati, 2014. Dark Matter Annihilation in the Universe. https://arxiv.org/abs/1403.4495 https://arxiv.org/abs/1403.4495
      - 3y ago
Quinner 3y ago
The authors are supposing that dark matter at this stage of the universe has its own particles and antiparticles and they are annihilating each other, the energy released by that annihilation is generating the heat.
- denton-scratch 3y ago
  Thanks, I wondered where this notion of "DM heating" came from, and why the DM "ran out". But if the DM runs out, then you'd expect the same to happen for non-DM matter, which it doesn't.
  - jeremyjh 3y ago
    Anti-matter is very rare with normal matter, so we don’t see it running out. But if dark matter and dark anti-matter are both just as common then you could see it play out as they suggest.
    - pfdietz 3y ago
      Some models of dark matter have the particles being their own antiparticles.
      - JumpCrisscross 3y ago
        Is it just charge that causes particles to have an antiparticle?
        pfdietz 3y ago
        No. Neutrons and antineutrons are different particles, for example.
        lanna 3y ago
        Neutrons don't have charge, but their quarks do. Antineutrons have quarks with reversed charge. Just like a neutral atom can have a neutral antiatom.

gnatman 3y ago

[flagged]

Pxtl 3y ago

I'm surprised to read an article with so much assumed knowledge about dark matter - about how it heats, etc. Is there a good place to read about the current best-guesses of the properties of dark matter?

dylan604 3y ago
Isn't the concept of dark matter just an assumption in itself? Seems to follow that any knowledge about it would be an assumption. In fact, that seems like good science, on instead of the word assumption, one might use theory. Once the theory is built up to test, it might actually one day become fact (or proven wrong).
- phkahler 3y ago
  The word they should be using is hypothesis, not theory. A theory stands up to scrutiny.
  - dylan604 3y ago
    there you go, an even better word. good thing i don't call myself a scientist
  - mr_mitm 3y ago
    That's not how the term "theory" is used in science. Only hobbyists care about the distinction, actual scientists infer the implied certainty from context. There is Born's rule, Noether's theorem, Newton's law (which we know is wrong), Einstein's theory of GR, the standard model (which is the best thing we have), ... sometimes we use the word "a quantum theory" to mean a certain Lagrangian, even one which we know does not describe reality at all.
    - consilient 3y ago
      > Noether's theorem is not like the other entries on your list. It's a full-blown mathematically rigorous theorem (that incidentally also happens to be of central importance in physics), not a physical model.

ajross 3y ago

Seems like a reasonably professional paper by real authors, but the abstract seems suspiciously handwavy while the content is a bit thick for me. Can we get a BS check from the physicists here? Is this a good area for inquiry or just mining a giant data set for confirmation of a wonky idea? Also: what's the "heating" mechanism proposed? Dark matter infall would pick up energy I guess, but if it's expected to interact only with gravity that doesn't seem likely to do anything meaningful vs. the same cloud contracting on its own? What's being heated?

samus 3y ago
There are two possible mechanisms referred to in the article: weakly interacting particles (WIMPs) or self-annihilating dark matter.

deleted 3y ago

[deleted]

fhars 3y ago

I sort of like the idea of a "dark star" shining "with up to ten billion solar luminosities"...

bongwater_OS 3y ago

They didn't need to use JWST to find a transcendental Dark Star, they could have just looked at Fillmore West in 1969.

jbotz 3y ago

So, IIUC, this is an alternative to the paper that was discussed a couple of days ago saying the Universe might be twice as old as previously thought. The "problem observations" both of them try to address are what appear to be huge galaxies at an early time (according to redshift) when there shouldn't have been such large galaxies yet. The aforementioned paper says maybe the Universe is actually much older. This paper says maybe those huge early galaxies aren't actually galaxies but "Dark Stars" instead.

neuralengine 3y ago

Not attempting to claim malfeasance or anything but PNAS has a weird "contributed article" track (this article is one of them) in which the authors _can pick their own reviewers_ [1]. "Only 18% of direct submissions were published in 2013, whereas more than 98% of contributed papers were published, according to figures on the journal's website" [2]. [1] https://www.pnas.org/author-center/member-contributed-submissions https://www.pnas.org/author-center/member-contributed-submis... [2] https://www.nature.com/articles/510330a https://www.nature.com/articles/510330a