While you're still able to edit your comment, you might consider something like quoting the relevant part of the article at the top:
"Some stars, though, have much more powerful fields [...] neutron stars have magnetic fields 1 trillion times stronger than the Sun’s. As the massive [progenitor] star collapses, its magnetic field lines are packed into a much tighter space, and the field strength increases. But then there are magnetars: These neutron stars have fields 1,000 times stronger [...] and, given that most stars aren’t all that magnetic to begin with, those are more difficult to explain."
Or indeed, from the subtitle near the very top:
"and it might explain the origin of highly magnetic cinders known as magnetars"
and then suggest your physics SE link (or rather, the accepted answer) for more information on the magnetic fields of neutron stars -- including theories about their origin as "fossils" of the progenitor star (like, but not quite as magnetic as, the star discussed in the article, which may offer support for the "fossil" theory) and internal dynamics during the collapse into the neutron star, or even after the neutron star has formed.
The accepted answer there <https://physics.stackexchange.com/posts/526296/revisions
> is a decent short read that is related to, and expands upon, the paragraph extracted above. However the answer and comments there are now several years old now, and are about an area of active research -- for example, one of the linked academic papers was less than a year old on the date the answer was submitted.
Or, perhaps you (and others) might do something like that next time, to do justice to an interesting and relevant link.
Finally, here is a link to the (open access) PDF of the paper published in Science, courtesy of the European Southern Observatory (and several of the authors' Canadian and European funding agencies): <https://www.eso.org/public/archives/releases/sciencepapers/e...>
It’s clearly about both. Don’t forget people post under different circumstances and may not have enough time or focus for quality highlights. Also, demanding curation barely motivates anyone. Just add what you think is missing.
I appreciated you sharing that relevant link about neutron stars and magnetic fields. Since the article is discussing a star with an unusually strong magnetic field that may help explain magnetars, readers might be interested to learn more details about neutron star magnetic fields too.
To help make the connection clearer, you could consider quoting a relevant excerpt from the article like:
"Some stars, though, have much more powerful fields [... ] neutron stars have magnetic fields 1 trillion times stronger than the Sun’s."
Then your physics stack exchange link provides some great additional details on theories about the origins of neutron star magnetic fields. The accepted answer there gives a nice short overview that expands on the article's point about how the star's collapse amplifies its field.
There's always more to learn about these complex astrophysical processes! I think your link makes a great addition, especially if you frame it as following up on the article's points. Let me know if you'd like any help editing your comment to connect the dots more clearly. Just wanted to provide a friendly suggestion, since I know I also appreciate feedback on how to improve my own comments sometimes.
I thought so, too. Upon a quick search, the most powerful magnet ever made on Earth is around 45 teslas, which according to WolframAlpha is 450,000 gauss. I'm assuming the difference is that these stars have the magnetic field strength everwhere on their surface and covering a huge region beyond the star, whereas the human made magnets, likely superconducting, only have that field strength in a very small area. That's just an intuitive guess though, as I don't know for sure.
Magnetic fields fall off with the inverse square law. A tiny magnet can easily be extremely powerful but it's very difficult for a huge one to be. Think of picking up a nail with a neodymium magnet and compare that with the earth's magnetic field affecting a compass needle.
The same rules apply to light. It's pretty easy to construct a light bulb with a filament which is hotter than the surface of the sun and which appears far brighter. But if you compare the sun and the light bulb at equal distances the sun is going to be brighter.
> Magnetic fields fall off with the inverse square law.
Inverse cube: the simplest magnets are dipoles.
> It's pretty easy to construct a light bulb with a filament which is hotter than the surface of the sun
The surface of the sun is about 10,000 F, well above the melting point of tungsten. Maybe there's some exotic ceramic that can survive those temperatures, but I'm not aware of any.
My favourite type of supernova is the pair-instability collapse, where it's hot enough that, thanks to the Maxwell-Boltzman distribution and Stefan–Boltzmann law, a nontrivial fraction of the photons spontaneously turn into positron-electron pairs, causing a runaway loss of pressure, leading to collapse, leading to more heat, leading to more sufficiently energetic photons… leading very quickly to multiple tens of solar masses of hydrogen turning directly into nickel-56 in a matter of seconds.
It sounds very interesting, like a scenario from https://what-if.xkcd.com/ but in real life. Do you know a good (not specialized) article/blog post/Wikipedia article about it? Something at the ELI25 level.
Check out Wolf-Rayet stars ([1]); effective surface temperature from 10,000 to 210,000 K. Tungsten melts at 3956 K, hafnium carbonitride ([2]) at 4370 K.
> Stable states are likely not all that hot, but what about supernova?
As context first, at some point temperature just sort of, stops being useful as a comparison. Not because it can't be computed, but because there really isn't any point of comparison for it. The coldest temperature in Antarctica was -89.2 Celsius [0]. The hottest day in Death Valley was 56.7 Celsius [1]. Tungsten melts at 3400 Celsius [2]. And papers about supernova will casually throw around phrases like "for temperatures exceeding a few 100 keVs" [3], to state that pretty much everything that happens in a supernova will be hotter than that. That's an energy measurement equivalent to about 1 trillion kelvin.
The second piece of context, for anything that deals with energy output, supernova are basically the "I win." answer. XKCD's "What If?" series has a good comparison for this, that for pretty much any comparison you can conceive, if the question is about energy output, the supernova wins.
> Which of the following would be brighter, in terms of the amount of energy delivered to your retina: (1) A supernova, seen from as far away as the Sun is from the Earth, or (2) The detonation of a hydrogen bomb pressed against your eyeball? ... [The supernova] is ... by nine orders of magnitude. [4]
So when temperatures are reported as 100 billion kelvin for the neutron star remnant [5], those are the cold (by comparison only) embers of a dying fire. The supernova itself has a "typical core temperature of 1 MeV" [3], which translates to about 10 trillion kelvin.
As the article describes, most star's magnetic field is rather steak. For example, the sun's magnetic field is only double the strength of Earth's. We have definitely built much stronger ones.
While it is not unusual for stellar objects to be magnetic, these are usually neutron stars. It is interesting to find something like this.
Inside of the Sun there are regions with significantly stronger fields. In particular the solar tachochline, a region at around 70% of the Sun's radius has fields of up to sometimes assumed 10 T. It's the region where the interior goes over to the convective zone. Due to differential rotation strong fields are produced.
I'm a bit doubtful of the 10 T number, having looked into literature about solar models ~5 years ago. More likely seems maybe 1-3 T, but maybe things are more clear now and I'm not an expert on solar magnetohydrodynamics (the strength there was just important for my work back then; but hey, if someone reads this who _is_ an expert, I'm still interested in details there haha).
The magnetic field of the star is measured by observing its plasma emissions? Or its effect on surrounding gases?
It sounds really fascinating, how does that work? In pictures you see a star only taking up a couple of pixels, so how much detail do you need to measure magnetic fields? Is that all done in radio astronomy?
Sorry for the machine gun questions but it's really interesting!
Almost all stars are point sources to us (i.e. they don't have a size), so you don't generally use a single image to get details. Instead you look at various wavelengths, though the use and combination of various optical devices (this is a whole massive field of research and engineering).
Radio astronomy looks at different wavelengths to optical astronomy, and because of atomic and molecular physics, you get different information.
If you're interested in this kind of stuff, go down to your local (university) library and see if you can borrow an undergrad introduction to astronomy (generally these will avoid most of the maths needed to actually do any work in the area, but cover enough of the concepts to be able to orient yourself in being able to look up stuff on wikipedia).
The electromagnetic field is the only one that is busy at all scales, from the atomic level, to stellar and even cosmological scales. Strong and electroweak forces dont have a macroscopic footprint, while gravity doesnt have a microscopic one.
So when gravity manifests around a mass agglomeration its somehow "normal". But when a strong magnetic field builds around a star is almost like the microscopic "leaking" into the macroscopic. Countless tiny electrons coordinated in a dance that can be seen across the universe.
33 comments
[ 4.2 ms ] story [ 82.9 ms ] threadWhile you're still able to edit your comment, you might consider something like quoting the relevant part of the article at the top:
"Some stars, though, have much more powerful fields [...] neutron stars have magnetic fields 1 trillion times stronger than the Sun’s. As the massive [progenitor] star collapses, its magnetic field lines are packed into a much tighter space, and the field strength increases. But then there are magnetars: These neutron stars have fields 1,000 times stronger [...] and, given that most stars aren’t all that magnetic to begin with, those are more difficult to explain."
Or indeed, from the subtitle near the very top:
"and it might explain the origin of highly magnetic cinders known as magnetars"
and then suggest your physics SE link (or rather, the accepted answer) for more information on the magnetic fields of neutron stars -- including theories about their origin as "fossils" of the progenitor star (like, but not quite as magnetic as, the star discussed in the article, which may offer support for the "fossil" theory) and internal dynamics during the collapse into the neutron star, or even after the neutron star has formed.
The accepted answer there <https://physics.stackexchange.com/posts/526296/revisions > is a decent short read that is related to, and expands upon, the paragraph extracted above. However the answer and comments there are now several years old now, and are about an area of active research -- for example, one of the linked academic papers was less than a year old on the date the answer was submitted.
Or, perhaps you (and others) might do something like that next time, to do justice to an interesting and relevant link.
Finally, here is a link to the (open access) PDF of the paper published in Science, courtesy of the European Southern Observatory (and several of the authors' Canadian and European funding agencies): <https://www.eso.org/public/archives/releases/sciencepapers/e...>
I appreciated you sharing that relevant link about neutron stars and magnetic fields. Since the article is discussing a star with an unusually strong magnetic field that may help explain magnetars, readers might be interested to learn more details about neutron star magnetic fields too.
To help make the connection clearer, you could consider quoting a relevant excerpt from the article like:
"Some stars, though, have much more powerful fields [... ] neutron stars have magnetic fields 1 trillion times stronger than the Sun’s."
Then your physics stack exchange link provides some great additional details on theories about the origins of neutron star magnetic fields. The accepted answer there gives a nice short overview that expands on the article's point about how the star's collapse amplifies its field.
There's always more to learn about these complex astrophysical processes! I think your link makes a great addition, especially if you frame it as following up on the article's points. Let me know if you'd like any help editing your comment to connect the dots more clearly. Just wanted to provide a friendly suggestion, since I know I also appreciate feedback on how to improve my own comments sometimes.
10,000 Gauss is 1 Tesla. 43,000 Gauss is 4.3T.
This does not sound impressive. What am I missing?
The same rules apply to light. It's pretty easy to construct a light bulb with a filament which is hotter than the surface of the sun and which appears far brighter. But if you compare the sun and the light bulb at equal distances the sun is going to be brighter.
Inverse cube: the simplest magnets are dipoles.
> It's pretty easy to construct a light bulb with a filament which is hotter than the surface of the sun
The surface of the sun is about 10,000 F, well above the melting point of tungsten. Maybe there's some exotic ceramic that can survive those temperatures, but I'm not aware of any.
But yeah. No filaments at that temperature, though 10,000F is rather easy to hit if you're not trying to keep whatever you're heating.
Though this does make me wonder how hot a star can get. Stable states are likely not all that hot, but what about supernova?
[1] https://en.wikipedia.org/wiki/Wolf%E2%80%93Rayet_star
[2] https://en.wikipedia.org/wiki/Hafnium_carbonitride
As context first, at some point temperature just sort of, stops being useful as a comparison. Not because it can't be computed, but because there really isn't any point of comparison for it. The coldest temperature in Antarctica was -89.2 Celsius [0]. The hottest day in Death Valley was 56.7 Celsius [1]. Tungsten melts at 3400 Celsius [2]. And papers about supernova will casually throw around phrases like "for temperatures exceeding a few 100 keVs" [3], to state that pretty much everything that happens in a supernova will be hotter than that. That's an energy measurement equivalent to about 1 trillion kelvin.
The second piece of context, for anything that deals with energy output, supernova are basically the "I win." answer. XKCD's "What If?" series has a good comparison for this, that for pretty much any comparison you can conceive, if the question is about energy output, the supernova wins.
> Which of the following would be brighter, in terms of the amount of energy delivered to your retina: (1) A supernova, seen from as far away as the Sun is from the Earth, or (2) The detonation of a hydrogen bomb pressed against your eyeball? ... [The supernova] is ... by nine orders of magnitude. [4]
So when temperatures are reported as 100 billion kelvin for the neutron star remnant [5], those are the cold (by comparison only) embers of a dying fire. The supernova itself has a "typical core temperature of 1 MeV" [3], which translates to about 10 trillion kelvin.
[0] https://en.wikipedia.org/wiki/Lowest_temperature_recorded_on...
[1] https://en.wikipedia.org/wiki/Highest_temperature_recorded_o...
[2] https://en.wikipedia.org/wiki/Tungsten
[3] https://arxiv.org/abs/astro-ph/0612072
[4] Xkcd, What If, #73: https://what-if.xkcd.com/73/
[5] https://en.wikipedia.org/wiki/Supernova#Detailed_process
While it is not unusual for stellar objects to be magnetic, these are usually neutron stars. It is interesting to find something like this.
Inside of the Sun there are regions with significantly stronger fields. In particular the solar tachochline, a region at around 70% of the Sun's radius has fields of up to sometimes assumed 10 T. It's the region where the interior goes over to the convective zone. Due to differential rotation strong fields are produced.
I'm a bit doubtful of the 10 T number, having looked into literature about solar models ~5 years ago. More likely seems maybe 1-3 T, but maybe things are more clear now and I'm not an expert on solar magnetohydrodynamics (the strength there was just important for my work back then; but hey, if someone reads this who _is_ an expert, I'm still interested in details there haha).
It sounds really fascinating, how does that work? In pictures you see a star only taking up a couple of pixels, so how much detail do you need to measure magnetic fields? Is that all done in radio astronomy?
Sorry for the machine gun questions but it's really interesting!
Almost all stars are point sources to us (i.e. they don't have a size), so you don't generally use a single image to get details. Instead you look at various wavelengths, though the use and combination of various optical devices (this is a whole massive field of research and engineering).
Radio astronomy looks at different wavelengths to optical astronomy, and because of atomic and molecular physics, you get different information.
If you're interested in this kind of stuff, go down to your local (university) library and see if you can borrow an undergrad introduction to astronomy (generally these will avoid most of the maths needed to actually do any work in the area, but cover enough of the concepts to be able to orient yourself in being able to look up stuff on wikipedia).
So when gravity manifests around a mass agglomeration its somehow "normal". But when a strong magnetic field builds around a star is almost like the microscopic "leaking" into the macroscopic. Countless tiny electrons coordinated in a dance that can be seen across the universe.