The only good kind of news about teslas in space.
July 15, 2022 11:55 AM Subscribe
"At a whopping 1.6 billion tesla, a pulsar called Swift J0243.6+6124 smashes the previous records of around 1 billion tesla, discovered surrounding the pulsars GRO J1008-57 and 1A 0535+262."
For context, magnets in a MRI are in the 1-3 tesla range; the earth's natural magnetic field is approximately 0.00003 tesla.
For context, magnets in a MRI are in the 1-3 tesla range; the earth's natural magnetic field is approximately 0.00003 tesla.
y'ever push the degauss button on a neutron star? I don't recommend it!
(this is tight. thank you for posting!)
posted by Eideteker at 12:06 PM on July 15, 2022 [3 favorites]
(this is tight. thank you for posting!)
posted by Eideteker at 12:06 PM on July 15, 2022 [3 favorites]
y'ever push the degauss button on a neutron star?
I bet that would make a really cool sound
posted by aubilenon at 12:20 PM on July 15, 2022 [3 favorites]
I bet that would make a really cool sound
posted by aubilenon at 12:20 PM on July 15, 2022 [3 favorites]
How to make a physicist swear in surprise: say “one billion teslas.”
A magnetic field has an energy density of u = B2/2μ0. For a billion tesla, this energy density is about 104 GeV/Å3, which about ten thousand times the energy density stored in the mass of an ordinary solid like ice. The magnetic field in the empty space around this pulsar is heavier than gold in roughly the same ratio that gold is heavier than air.
This astounding mass-energy density is, however, a part-per-trillion correction to the mass density of the nuclear matter that makes up the neutron star itself.
posted by fantabulous timewaster at 12:49 PM on July 15, 2022 [15 favorites]
A magnetic field has an energy density of u = B2/2μ0. For a billion tesla, this energy density is about 104 GeV/Å3, which about ten thousand times the energy density stored in the mass of an ordinary solid like ice. The magnetic field in the empty space around this pulsar is heavier than gold in roughly the same ratio that gold is heavier than air.
This astounding mass-energy density is, however, a part-per-trillion correction to the mass density of the nuclear matter that makes up the neutron star itself.
posted by fantabulous timewaster at 12:49 PM on July 15, 2022 [15 favorites]
I once had a chance to visit a colleague at a facility with a 10 Tesla MRI scanner (fairly rare, used only for research). There's a fun demonstration of Lenz's law that you can do with aluminum hoops near the bore of an MRI, showing how the eddy currents induced in the hoop as it moves through the magnetic field create a force resisting the movement. Here's an example with a more standard medical 3T scanner. With a 10 T scanner, I got to watch as my colleague struggled against apparently nothing to force the hoop into position, then watch as the hoop hung suspended in space, slowly sinking as if the air were made of honey. It's one of those things that if you know the physics, is entirely predictable and comprehensible, yet actually seeing it happen in front of your eyes still feels like a magic trick.
I'm not quite sure what a billion Tesla would do to a 1 meter aluminum hoop, but I suspect it would instantly melt and get shredded to pieces at the slightest movement.
posted by biogeo at 12:58 PM on July 15, 2022 [5 favorites]
I'm not quite sure what a billion Tesla would do to a 1 meter aluminum hoop, but I suspect it would instantly melt and get shredded to pieces at the slightest movement.
posted by biogeo at 12:58 PM on July 15, 2022 [5 favorites]
Yeah, when we talk about space weather, when the Earth's magnetic field gets affected electrical grid operators start looking at potential problems. This is due to deflections in the field that they measure in nanoTesla. The Quebec grid shutdown in the 80s was due to a geomagnetic storm measuring something like 500 nanoTesla, or about half of a milliTesla.
1.6 gigaTesla is, as fantabulous timewaster says, enough to make this dude with an Astrophysics degree say "holy shit."
posted by tclark at 1:01 PM on July 15, 2022
1.6 gigaTesla is, as fantabulous timewaster says, enough to make this dude with an Astrophysics degree say "holy shit."
posted by tclark at 1:01 PM on July 15, 2022
Don't forget that this city-sized pulsar is spinning around on its axis. If I've followed the correct link from the technical article, the pulsar has the rather stately rotation period of one turn every ten seconds.
If you are a person who like physics demos, you can do biogeo's eddy-current demonstration by dropping a strong magnet through a copper pipe. The aluminum hoop next to the MRI is really something else, though.
posted by fantabulous timewaster at 1:19 PM on July 15, 2022 [1 favorite]
If you are a person who like physics demos, you can do biogeo's eddy-current demonstration by dropping a strong magnet through a copper pipe. The aluminum hoop next to the MRI is really something else, though.
posted by fantabulous timewaster at 1:19 PM on July 15, 2022 [1 favorite]
Also apropos of nothing in particular, if you wanted to do an MRI in the pulsar's magnetic field, you'd need to use ultraviolet light instead of radio waves in order to get the required nuclear magnetic resonance. More realistically, I guess that means that hydrogen must "fluoresce" in the ultraviolet due to Larmor precession in such strong magnetic fields. Wild to think about.
posted by biogeo at 1:23 PM on July 15, 2022
posted by biogeo at 1:23 PM on July 15, 2022
A regrettable effect of Elon Musk on my brain - the first thought I had when I read "1.5 billion teslas" is "Gee, that's a lot of traffic."
posted by storybored at 1:37 PM on July 15, 2022
posted by storybored at 1:37 PM on July 15, 2022
The magnetic field in the empty space around this pulsar is heavier than gold in roughly the same ratio that gold is heavier than air.
Hold up, am I reading this correctly, the power of the magnetic field in the space around the pulsar has weight? As in, the space itself is heavy? I have no astrophysics degree whatsoever, so I'm not being sarcastic when I say... WHA?
posted by The Pluto Gangsta at 2:13 PM on July 15, 2022 [1 favorite]
Hold up, am I reading this correctly, the power of the magnetic field in the space around the pulsar has weight? As in, the space itself is heavy? I have no astrophysics degree whatsoever, so I'm not being sarcastic when I say... WHA?
posted by The Pluto Gangsta at 2:13 PM on July 15, 2022 [1 favorite]
In general relativity, all forms of energy contribute to gravitational fields. When light rays are deflected in the gravitational field of the Sun, the Sun is also pulled in the direction of the passing light rays. Just not as much. Like, a lot not as much.
All magnetic fields therefore have "weight," in the sense that they contribute to gravitation. If you buy a nice strong neodymium magnet from the hardware store, the field right at its surface might actually be roughly a tesla. (It falls off really fast with distance.) But a billion is a huge factor, and a billion-squared is huge-squared. A field of strength one tesla has stored energy which contributes to gravitation, but not very much.
(I haven't ever done this calculation before, and now I'm worried that I've made a mistake — for a one-tesla field, I find an energy density comparable to a mass density of ten-ish nanograms per cubic meter. Which is small, but not nearly as small as I would have guessed. A one-tesla field has more energy density, for instance, than the mass associated with the interplanetary medium, where there is about one hydrogen atom per cubic centimeter. Perhaps another person who likes unit conversions can double-check my arithmetic. I hate making errors in exponents, and I do it all the time.)
posted by fantabulous timewaster at 2:48 PM on July 15, 2022 [1 favorite]
All magnetic fields therefore have "weight," in the sense that they contribute to gravitation. If you buy a nice strong neodymium magnet from the hardware store, the field right at its surface might actually be roughly a tesla. (It falls off really fast with distance.) But a billion is a huge factor, and a billion-squared is huge-squared. A field of strength one tesla has stored energy which contributes to gravitation, but not very much.
(I haven't ever done this calculation before, and now I'm worried that I've made a mistake — for a one-tesla field, I find an energy density comparable to a mass density of ten-ish nanograms per cubic meter. Which is small, but not nearly as small as I would have guessed. A one-tesla field has more energy density, for instance, than the mass associated with the interplanetary medium, where there is about one hydrogen atom per cubic centimeter. Perhaps another person who likes unit conversions can double-check my arithmetic. I hate making errors in exponents, and I do it all the time.)
posted by fantabulous timewaster at 2:48 PM on July 15, 2022 [1 favorite]
The magnetic field contains energy. And by E=mc^2, any area of space containing energy literally has corresponding mass. But since m=E/c^2, that’s a staggering amount of energy.
posted by sjswitzer at 2:51 PM on July 15, 2022
posted by sjswitzer at 2:51 PM on July 15, 2022
The mass of energy isn't just an exotic thing that happens in extreme situations. Only about 1% of the mass of everyday matter is due to the inherent mass of its constituent particles; the remaining 99% is due to the energy binding the particles together!
For neutrons, the sum of the rest masses of the three valence quarks (two down quarks and one up quark) is approximately 11.9 MeV/c2, while the neutron's total mass is about 939.6 MeV/c2. Considering that nearly all of the atom's mass is concentrated in the nucleons, this means that about 99% of the mass of everyday matter (baryonic matter) is, in fact, chromodynamic binding energy. -- Wikipediaposted by sjswitzer at 3:12 PM on July 15, 2022 [2 favorites]
Question for the astrophysicists: does the energy stored in the magnetic field near one of these extreme objects (pulsar, supermassive black hole, etc.) have an appreciable effect on the gravitational field near the object, then? Naively, with intuitions based mostly on classical mechanics, I would think this would "spread" some of the mass associated with the object out a bit, such that if you weren't accounting for it, the fall-off of gravitational field strength with distance from the surface of the object wouldn't look quite inverse-square any more. Or perhaps the "conventional" mass of the object is so much higher than the energy density of the magnetic field that this just ends up being a negligible correction term?
posted by biogeo at 3:32 PM on July 15, 2022
posted by biogeo at 3:32 PM on July 15, 2022
*grimaces at seeing the B Field reported in T and not G*
posted by miguelcervantes at 3:40 PM on July 15, 2022
posted by miguelcervantes at 3:40 PM on July 15, 2022
Not an astrophysicist, but you are correct on both counts. Although it has twice the mass density of gold(!) that's practically nothing compared to neutronium.
But also, as you suspect, being diffuse matters too. If we imagine, contrary to fact, this mass/energy were smoothly distributed then, due to the Shell Theorem, if you draw a sphere centered on the center of the neutron star and with the observer on the surface, then the observer experiences attraction only to the mass inside the sphere. Everything outside the sphere cancels out! (With, no doubt, some complications from General relativity, but the general principle stands.)
posted by sjswitzer at 3:42 PM on July 15, 2022 [3 favorites]
But also, as you suspect, being diffuse matters too. If we imagine, contrary to fact, this mass/energy were smoothly distributed then, due to the Shell Theorem, if you draw a sphere centered on the center of the neutron star and with the observer on the surface, then the observer experiences attraction only to the mass inside the sphere. Everything outside the sphere cancels out! (With, no doubt, some complications from General relativity, but the general principle stands.)
posted by sjswitzer at 3:42 PM on July 15, 2022 [3 favorites]
biogeo: Within the neutron star, like I said already, the magnetic field is a tiny correction to the mass density.
Outside of the neutron star, the field is a “dipole,” and gets smaller like distance cubed from the center. This means the energy density goes like distance to the sixth power. That falls of much, much faster than the volume enclosed in the sphere, so nearly all of the field’s contribution to the total energy comes from the strongest field inside and just outside of the star.
posted by fantabulous timewaster at 3:44 PM on July 15, 2022 [4 favorites]
Outside of the neutron star, the field is a “dipole,” and gets smaller like distance cubed from the center. This means the energy density goes like distance to the sixth power. That falls of much, much faster than the volume enclosed in the sphere, so nearly all of the field’s contribution to the total energy comes from the strongest field inside and just outside of the star.
posted by fantabulous timewaster at 3:44 PM on July 15, 2022 [4 favorites]
(I made an oopsie above, saying the mass density was twice that of gold. I must have misread or misremembered something above. It's much more than that. I refer you back to fantabulous timewaster's comment for an informed and accurate description.)
posted by sjswitzer at 4:59 PM on July 15, 2022 [1 favorite]
posted by sjswitzer at 4:59 PM on July 15, 2022 [1 favorite]
For the actual experts here, the magnetic fields here must be insanely twisted and tangled. Do the twists and tangles embody any energy themselves or do they just lend themselves to crazy flux rope shenanigans?
posted by sjswitzer at 5:08 PM on July 15, 2022
posted by sjswitzer at 5:08 PM on July 15, 2022
Only about 1% of the mass of everyday matter is due to the inherent mass of its constituent particles; the remaining 99% is due to the energy binding the particles together!
Mind Blown.
Does magnetic fields having weight mean that when we juice a good size electromagnet it gets heavier?
posted by Mitheral at 6:07 PM on July 15, 2022
Mind Blown.
Does magnetic fields having weight mean that when we juice a good size electromagnet it gets heavier?
posted by Mitheral at 6:07 PM on July 15, 2022
Yes, an energized electromagnet is heavier than one that’s off. But not measurably. One-ish tesla is the magnetic field you get if there is one aligned electron per atom in an ordinary-density solid. One tesla in free space is the nanograms per cubic meter energy density I referred to above (thanks for the double-check, sjswitzer).But in iron you have a much larger permeability μ than in vacuum, so the energy density associated with the field is reduced down to femtograms per cubic meter. A tiny, tiny correction to the mass.
In order to have a “tangled” magnetic field in free space, like near sunspots, you have to account for the motions of charged particles in the plasma, which move in helices around the magnetic field lines but also reinforce the magnetic field because they are moving charges. Plasma physics is a super-complicated field that I don’t know much about.
posted by fantabulous timewaster at 7:06 PM on July 15, 2022 [2 favorites]
In order to have a “tangled” magnetic field in free space, like near sunspots, you have to account for the motions of charged particles in the plasma, which move in helices around the magnetic field lines but also reinforce the magnetic field because they are moving charges. Plasma physics is a super-complicated field that I don’t know much about.
posted by fantabulous timewaster at 7:06 PM on July 15, 2022 [2 favorites]
Something that just occurred to me is that the conventional wisdom that nuclear energy is "converting matter to energy" is "mostly wrong." In general, fusion and fission don't significantly alter the constituent subatomic particles (modulo beta decay, etc.; the weak force is the joker card in the particle deck) but rather just release the binding energy that's left over after rearranging the matter particles (fermions) into less energetic configurations.
Edit: But I hasten to add that these reconfigurations of course reduce the mass of the remaining matter. It's just that the reduced mass is less binding energy.
posted by sjswitzer at 7:29 PM on July 15, 2022 [2 favorites]
Edit: But I hasten to add that these reconfigurations of course reduce the mass of the remaining matter. It's just that the reduced mass is less binding energy.
posted by sjswitzer at 7:29 PM on July 15, 2022 [2 favorites]
For those of you who like video explanations, PBS Space Time has an excellent video on how mass arises as "confined energy" if you will. There's also a very good video on neutron stars (of which pulsars are one type). If you're enjoying having your mind blown by this discussion, I expect you'll also enjoy having your mind blown by those videos.
posted by biogeo at 8:12 PM on July 15, 2022 [4 favorites]
posted by biogeo at 8:12 PM on July 15, 2022 [4 favorites]
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