Can someone explain this science/astronomy pic?

Question

Mainly the hot plasma part. And why it's magnitized. And if you can those accreation disks.

http://www.astro.umd.edu/~miller/Images/Accreting-Neutron-Star.jpg

Answer 1

Let's start with the accretion disk. When a more-or-less spherical mass of gas and dust is rotating, two forces are present. First, the matter begins to collapse toward the center due to gravity. This movement toward the center is counteracted by the centrifugal force of the rotation. But the centrifugal force is not equal around the sphere: it's zero at the pole of rotation and maximum at the "equator" of rotation. That means that at the pole of rotation the collapse to the center is fastest, and so the sphere flattens out into a disk. That's what is called an accretion disk, and they are rather common in the universe; it is believed that our Solar System started out as an accretion disk, for example. That's why all the planets orbit in nearly the same plane.

In the diagram, we have a neutron star surrounded by an accretion disk. Neutron stars are very small and very dense, falling just short of becoming a black hole. They also have very, very intense magnetic fields. In the diagram, the poles of the magnetic field are not aligned with the rotation axis of the neutron star itself. (This is also quite common; the Earth's magnetic field isn't quite aligned with the axis either.) The magnetic field is so strong that it is able to strip electrons away from atoms in the accretion disk. When that happens, the disk becomes a "plasma", which is a gas that is ionized, and therefore follows magnetic field lines.

As the strong gravity pulls the matter of the accretion disk inward, the strong magnetic field (black lines) forces the plasma in the disk (red) to follow the magnetic field lines toward the magnetic poles of the neutron star (red arrows). As this matter continues to fall inward, the magnetic field lines converge and the plasma is compressed into a very tiny area, becoming very hot in the process. This hot matter then emits very strong radiation as it dives toward the magnetic pole of the neutron star.

Because the magnetic axis is not aligned with the rotation axis, the magnetic poles rotate as the neutron star rotates (which is very fast). There are two "hot spots" of emission at the magnetic poles from the infalling matter, and as the star rotates these hot spots rotate too, causing the radiation of the neutron star to fluctuate very rapidly. This is called a pulsar.