I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
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@trrektor
If light speed were zero humans would not exist and not have arms.
@vicgrinberg@notsoloud @vicgrinberg nah in this example it's turned to zero while existing
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg How much impact does dark matter have on stars? (Does the extra gravity influence internal processes, the number of CMEs, etc.) How much does it vary based upon the star's size? Is there the same relative regular matter to dark matter ratio regardless of size?
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg Maybe more of a physics question than a star question; if so, I apologize: what is your take on the new possibility that black holes may not contain singularities after all?
https://www.sciencenewstoday.org/no-more-singularity-physicists-propose-new-black-hole-paradigms
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg How rare is gold in the universe.
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
Since I have not seen the question already: What are those winds you mentioned? How can I imagine them? I suspect stars don't have an atmosphere like planets do.
I am so confused.
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@johnnythan thanks for boosting - and it's also interesting for me to know that folks know nothing about stars. I'm so used to people knowing a lot about them in my everyday life
@vicgrinberg @johnnythan This XKCD is more accurate than one might think. I've been guilty of it too.
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@quixoticgeek it's going to be pretty much the same - the stars are very far away and our atmosphere very thin, so get to outside of it does not change much in what we see. What we get rid off are the effect of the atmosphere - the twinkling is because of atmospheric effects (similar effect to warm air above a hot street), the stars themselves don't twinkle! So the view is in a way clearer.
@vicgrinberg In this year of our lord 2026 with that monstrosity in office I did not need to know that not only will there be no shining city on the hill if we can’t get the votes to save democracy but the stars don’t actually twinkle. @quixoticgeek
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg I've always thought the ability of gas & plasma to sustain shockwaves means they can actually carry sound.
one of the more spectacular examples would be the "bounce" of core collapse in a supernova. but years and years after that, the shockwave is still travelling and the gas density is very thin.
does that mean these thin clouds of gas can carry sound? are the remnants dense enough to carry it? your work is with stellar winds, does it have sound? does a corona carry sound? the gas "leak" from a cataclysmic variable, what about that...
(I am not a professional astrophysicist, but I sure wanted to be one.)
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg I know this may go unnoticed. Which is fine. Totally fine. At least I'm willing to try. Anyways, this is how I describe the physics of the Milky Way galaxy in the natural Universe. Is this:
Galaxies hold shape and rotation due to the Tropic Field Extremum's gravitational entrainment upon the stellar mass that is stabilized by the angular momentum trajectory of the host galaxy.
**Tropic Field Extremum**: is the gravitational "bowl" (not) a singularity. Like a skate bowl at a park. -
@Enema_Cowboy likely yes - but it's not that simple, eg NASA's Juno found that Jupiter core is rather "fuzzy" and not just a ball of heavy elements https://science.nasa.gov/jupiter/jupiter-facts/
@vicgrinberg Wow, I'm amazed that the structure of core could be detected.
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
I heard Brian Cox talk about “escape velocity” in relation to density. What are the densest objects discovered and how dense are they?
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg Perhaps more a quantum physics question than astrophysics, but: I never understood why fusion stops releasing energy at iron, and you start to need more energy than you get out if you fuse nuclei together above that weight.
The star lifecycle explanations I've run across in the past don't go deeper than "it just does", but is there a deeper reason?
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg
Bussard ramjets still impossible?
Solar sails possible? -
I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg
This could be a question specific to stars (or even specific to massive stars) or it could be a question for all of astrophysics, I guess. Are we collecting data about the universe and its. contents faster than we (meaning you astrophysicists primarily) can analyze it? I know there are citizen science projects that help to classify galaxies and whatnot (Galaxy Zoo? I don't remember) but I imagine the flood of data far outstrips the ability of humans to parse it all. True? Are we getting ever further behind? -
@vicgrinberg Perhaps more a quantum physics question than astrophysics, but: I never understood why fusion stops releasing energy at iron, and you start to need more energy than you get out if you fuse nuclei together above that weight.
The star lifecycle explanations I've run across in the past don't go deeper than "it just does", but is there a deeper reason?
@Two9A to be honest, I don't know what you mean by a deeper reason here. There is no reason why things are the way they are - except that we would not exist as we are if they weren't.
For atoms, you can roughly imagine that the more (positivly charged) protons there are, the harder it is to squeeze them together. So the larger the atom, the less energy is left over to be released when it is created, until at some point you need go add energy to make them instewd of releasing.
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I heard Brian Cox talk about “escape velocity” in relation to density. What are the densest objects discovered and how dense are they?
@DaveNelson it's not a about stars, but I'll answer (I like neutron stars & black holes): the densest objects of normal matter are neutron stars - pretty much the density of an atomic nucleus but as a star or the mass of 1.4 suns squeezed into a ball of 10 km radius. Denser doesn't work - if we pile up more than 3 sun masses together at neutron star density or squeeze the neutron star further, we end up with a black hole, where things collapse to endless density in a singularity in the middle.
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@vicgrinberg I've always thought the ability of gas & plasma to sustain shockwaves means they can actually carry sound.
one of the more spectacular examples would be the "bounce" of core collapse in a supernova. but years and years after that, the shockwave is still travelling and the gas density is very thin.
does that mean these thin clouds of gas can carry sound? are the remnants dense enough to carry it? your work is with stellar winds, does it have sound? does a corona carry sound? the gas "leak" from a cataclysmic variable, what about that...
(I am not a professional astrophysicist, but I sure wanted to be one.)
@draNgNon this is not a question about stats, so very short answer: gas clouds are far too thin to carry sound in the meaning of the sound on Earth - the densest gas clouds are as dense as some of the most extreme vacuums we can create on Earth. The Universe is very, very empty.
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg Do you think it is possible to verify models in theoretical physics using publicly available data from repositories such as https://researchguides.gonzaga.edu/physics/data only ? Just order this data around some N real world physical experiments and check your theoretical physics model for each of the N experiments. My idea is developing new models in theoretical physics using AI (new geometries in general relativity for example) and check them against the public data repos.
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@Two9A to be honest, I don't know what you mean by a deeper reason here. There is no reason why things are the way they are - except that we would not exist as we are if they weren't.
For atoms, you can roughly imagine that the more (positivly charged) protons there are, the harder it is to squeeze them together. So the larger the atom, the less energy is left over to be released when it is created, until at some point you need go add energy to make them instewd of releasing.
@vicgrinberg Fair, I guess it's a question along the lines of "what if G had a different value": not something one can answer except with "in this universe it doesn't".
Thanks for taking the time!
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Since I have not seen the question already: What are those winds you mentioned? How can I imagine them? I suspect stars don't have an atmosphere like planets do.
I am so confused.
@palaress ah, thanks for the question! Stellar wind (our Sun also has a wind, called solar wind) is not something that happens in an atmosphere, but rather a thin stream of particles blown away from the star from its uppermost layers. Stellar wind is what makes Aurorae (when there is an especially strong bit of it) and that makes comets have nice tails (the tail is pretty mucbtan interaction result of the comet with the wind).
