The final end products of stars are really extreme. Stars like the Sun end up as “white dwarfs”, where the exposed core of the former star is left behind, and about 60% of the total mass of the star is jammed into something the size of the Earth. A spoonful of a white dwarf would weigh about 1 ton (here on earth). Stars much more massive than the Sun end their lives as black holes. Good luck getting a black hole on a spoon. Its gravitational force would be so intense, the molecules that compose the spoon, your hand, and your arm would be shredded apart. In between black holes and white dwarfs are objects called neutron stars. They are much more dense than white dwarfs. One spoonful of a neutron star would weigh about 1 billion tons. Which raises some interesting questions.
See, neutron stars are really just a large clump of neutrons being acted upon by mainly two forces. Gravity is one of them, and its trying to collapse the star upon itself. The other force is something called degeneracy pressure, which is a result from quantum mechanics. It only comes into play when you have a lot of the same atomic particles in the same place (like a neutron star or a white dwarf). The bottom line is that there is a lot of interesting physics going on in these stars, and they are attractive targets for observers and theorists.
In a paper titled “A r-mode in a magnetic rotating spherical layer: application to neutron stars”, S. Abbassi, M. Rieutord and V. Rezania present some theoretical models of neutron star surfaces. It turns out, that even at these high densities, there can be oscillations induced in the surface of the neutron star. The “r-mode” is a horizontal wave. If the neutron star is like a globe, these would be waves of constant longitude, sloshing back and forth horizontally. These types of waves are also thought to occur in the Earth’s core. What Abbassi and collaborators set out to do in this paper was to examine the effects of magnetic fields on these pulsations. Specifically, they wanted to know if magnetic fields might be strong enough to induce these oscillations. Their work suggests that this is not the case though. The field strength necessary to induce oscillations in their model was roughly 100 times larger than what is observed in typical neutron stars. But this type of work is critical for understanding what happens to matter in these extreme conditions.