This Wiki article claims that the surface of this pulsar, at it’s equator, is spinning at a quarter of the speed of light. That’s seems incredibly fast for ordinary matter to be to be moving, much less revolving around a very tight radius.
Is it just the incredible denseness that keeps it from flying apart? If it slowed down would it become a black hole?
Really interesting! My quick, back-of-the-envelope calcs using the Wikipedia-provided values give me:
vs
So… the gravity force is about 2000 times greater than needed to keep the star together. Of course, I’m not including anything fancy like relativity.
Yes. It’s useful to keep in mind that on the scale of planets and stars, tensile strength effectively doesn’t exist and objects can be treated as droplets of liquid for such questions as “why are they that shape” and “how do they hold together”.
Wow. Thanks.
Also, pretty much all of the numbers associated with pulsars are huge beyond human imagining. Like, in some pulsars, the magnetic field has a density ten thousand times as great as lead. Not the matter of the star; literally just the magnetic field.
I’ve been trying to understand that since you posted it. Even googling and reading up on it doesn’t really help much.
AI overview:
The magnetic field energy surrounding a neutron star—specifically a magnetar—possesses an energy density that is profoundly greater than the physical density of lead.
- Mass Density of Magnetar Magnetic Fields: The magnetic field of a magnetar can reach intensities of 1010Tesla (or higher), which results in an energy density (E/c2) more than 10,000 times greater than the physical density of lead.
- Physical Density of Lead: Lead has a density of approximately 11.34 g/cm³.
- Neutron Star Density: A teaspoon of neutron star material, regardless of its magnetic field, already weighs about 10 million tons.
- Magnetic vs. Material Density: The energy stored in the magnetic field of a magnetar is so high that it can deform atoms into thin cylinders and polarize the vacuum itself.
- Theoretical Comparison: This magnetic field energy density is so intense that it is suggested to be one of the only things in the universe (other than a black hole) that can store energy at a higher density than ordinary physical matter.
I’m trying to picture what that gravity field would look like? !s it still transparent (like gravity fields on earth) or is it more like a solid?
Correction, Magnetic field - not gravity field.
That is interesting. Some stars spin so rapidly that they become flattened (oblate), like M+Ms; Regulus and Achernar are examples.
Despite spinning much more rapidly than Achernar, a typical magnetar is hardly oblate at all
A nice animation here.
NASA SVS | Migrating Magnetar Hot Spot Animations.
Trapped particles and starquakes in this field would produce brilliant flashes of X-rays, so I really don’t think you’d want to get close enough to see the surface in any detail.
A quote from Wikipedia on Magnetars, the term for this subtype of pulsars.
As described in the February 2003 Scientific American cover story, remarkable things happen within a magnetic field of magnetar strength. “X-ray photons readily split in two or merge. The vacuum itself is polarized, becoming strongly birefringent, like a calcite crystal. Atoms are deformed into long cylinders thinner than the quantum-relativistic de Broglie wavelength of an electron.”
If even x-rays are being messed up, I doubt visible light would get through without being wildly distorted.
OK, you know how matter can be converted to energy? Well, it’s not really converted: Matter is always energy. We just don’t think of it as such, because it’s so much denser than most other forms of energy we encounter.
Most. But electromagnetic fields also contain energy. And the electromagnetic fields in a magnetar are so ludicrously strong, that they contain energy much denser than any sort of what we’d call “normal” matter.
That AI overview is wrong, though: Magnetic fields that strong cannot polarize the vacuum, because doing that would require producing magnetic monopoles, and magnetic monopoles are way too massive. An electric field of comparable magnitude probably would polarize the vacuum, but you only need electrons (much lighter) in order to do that.
The Scientific American quote used the term too, and googling it does seem like magnetic fields can polarize the vacuum.
Vacuum Polarization by a Magnetic Field and its Astrophysical Manifestations