[_Microft]

Magnetars are even more mindblowing than blackholes, in my opinion.

Here is an excerpt from the Wikipedia article on Magnetars, to blow your mind as well:

"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." In a field of about 10^5 Tesla atomic orbitals deform into rod shapes. At 10^10 Tesla, a hydrogen atom becomes a spindle 200 times narrower than its normal diameter., from https://en.wikipedia.org/wiki/Magnetar

Edit:

"Die Massendichte, die einem derartigen Magnetfeld über seine Energiedichte in Kombination mit der Äquivalenz von Masse und Energie gemäß E = m c^2 zugeordnet werden kann, liegt im Bereich einiger Dutzend Kilogramm pro Kubikmillimeter (kg/mm3)", from german Wikipedia, https://de.wikipedia.org/wiki/Magnetar#Entstehung

says that the mass density (via energy-mass equivalence) of such strong magnetic fields might be dozens of kilograms per cubic millimeter (kg/mm^3).

Mind. Blown.

[SirLuxuryYacht]

How do those rod-shaped atoms, like hydrogen, interact with other hydrogens or other atoms? Can chemical reactions still even happen in the traditional sense?

[robocat]

The temperature is expected to remain above plasma temperatures even if a neutron star could cool for a billion years, so presumably normal chemistry couldn’t occur.

https://astronomy.stackexchange.com/questions/14387/what-hap...

The coldest neutron star detected “T < 42,000 Kelvin” : https://arxiv.org/abs/1901.07998

Disclaimer: I am not an astrophysicist.

[yk]

Depends, chemistry looks very differently simply because in such environments it is better to think of an electron gas that moves in a magnetic field, and is slightly perturbed by the presence of nuclei, rather than thinking of electrons being bound in atoms and being slightly perturbed by a magnetic field.

So you certainly have to recalculate all your reaction rates compared to laboratory conditions, and my guess would be, that in general the chemistry should look a lot more than reactions in plasmas, rather than normal (nicely stable) chemistry.

[DecoPerson]

Layman here.

Most classes of stars are already hot enough that molecules are torn apart. The atoms are in a gas or plasma state. Pairs of atoms will pass through transient states that could be classed as “molecules” but they’re very short-lived. Electrons—a key part of chemical reactions—flow freely like in metal.

Hydrogen atoms are just a single proton with some number of neutrons. I’m not sure if the proton itself is stretched (Is a gluon a particle like a proton is a particle??), or if the EM field around the proton is so influenced that electrons move around it like it’s a rod/cylinder.