Neutron Star

Neutron Star captured without auto exposure in SpaceEngine.

Neutron Star is a kind of "Compact Star", its mass is 1.35 to 2.1 M☉ (1.35 to 2.1 times the mass of the Sun), and its diameter is a few kilometers (20 kilometers approximately), Therefore it's a object very dense and its gravitational field is too strong.

It originates from the gravitational collapse of a main sequence star with a lot of mass, as a Blue supergiant. When a massive star has a supernova explosion the star collapses by its own weight, then its diameter decreases.

(In the picture: As this object has a very strong gravitational field visible light from the Milky Way and the stars behind it is deviates)

Life cycle of a dwarf star and a massive star.

Neutron Stars are formed manly by neutrons, also have other types of particles inside and they are considered degenerate matter because much of their pressure comes from the Pauli exclusion principle.

Some Neutron Stars are Pulsating Radio Stars (Pulsar), they  emit a beam of electromagnetic Radiation, these emissions are moved due to the rotation of the star and are produced due to the matter that the star absorbs its accretion disk.

Revolving around of PSR B1509-58 (And its accretion disk), this GIF is taken with SpaceEngine
(The beam of electromagnetic radiation emitted by the star isn't visible from this capture).

"Artistic representation" of a pulsar. This GIF is Taken With Universe Sandbox.
This image shows the beam of electromagnetic radiation emitted by a Pulsar, but it isn't realistic.