When a massive star uses up its nuclear fuel, there is no longer enough heat to hold up its core against gravitational forces, and the core collapses. The result is an explosion, called a supernova, which leaves behind a very dense core, called a neutron star.
A neutron star is composed mainly of neutrons. It has approximately the mass of the Sun, but the radius is about 14 km, that is, 50,000 times smaller than the Sun's. The structure inside a neutron star is different from anything known on Earth, and the gravity on the surface is strong enough to crush any ordinary material. The only thing which creates a stronger gravitational field is a black hole.
Away from the surface, the tidal forces near a neutron star are nevertheless prodigious. A man falling toward a neutron star would be stretched out as he fell. He would be killed when he was about 2000 km away, and as he got closer he would be drawn as thin as a wire. Finally he would land on the surface, creating a shower of X-rays.
For these problems you may want to use the following:
G = 6.67 x 10–11 N m2/kg2
MSun = 2.0 x 1030 kg
Vsphere = 4/3 π r3 (volume of a sphere)
Asphere = 4π r2 (surface area of a sphere)
Acircle = π r2 (area of a circle)
What is the approximate density of a neutron star?