Neutron Stars: Holy Shit

The average neutron star weighs 40% more than our sun, and is the result of a star weighing more than 8 solar masses going supernova. Any lighter, and it would be a white dwarf. Anything heavier would create a black hole. The interesting thing about neutron stars is they're only 25 km wide, about the size of Manhattan.

As you might imagine, the resulting density has some pretty weird effects. A teaspoon of material from a neutron star would weigh a billion tons. Its escape velocity is half the speed of light (150,000 km/second), so if you began to fall towards it, it would be pretty difficult to escape. Electrons and protons are forced together into neutrons, hence the name, and its surface temperature is over 1.8 million °F. Because the original star's angular momentum is conserved, a neutron star spins very quickly. "Very quickly" ranges from several seconds per rotation to a theoretical maximum of 3000 rotations per second, after which it would fly apart.

The fastest observed neutron star (PSR B1937+21) rotates 641 times per second. With a diameter of 25 km, this means its surface is moving at one-sixth of c. A neutron star spinning 3000 times per second would have a surface speed nearly four-fifths of c. Neutron stars also have extremely strong magnetic fields, and emit powerful beams of charged particles from their magnetic poles. Since the magnetic poles aren't located at the rotational poles, these beams of radiation sweep through space as if they were attached to some insane killer lighthouse. When these beams are visible to us, the neutron star is referred to as a pulsar. Actual recordings of pulsars can be found here. They give a pretty good sense of how quickly the star is spinning.

The magnetic field of an average neutron star slows its rotation by radiating energy, but it takes millions of years to slow down by a fraction of a second. As you can see, these spinners don't stop, and may even increase in speed due to accretion of material from a companion star. Another class of neutron stars, known as magnetars, has an abnormally strong magnetic field and a long rotational period. It is theorized that the field is generated by convection currents in the star's interior, and it is this same field that causes the star to lose rotational speed at an accelerated rate. Massive starquakes blast matter and energy away rapidly; in December of 2004, a gamma ray burst from a magnetar 50,000 light years away (SGR 1806-20) was strong enough to briefly expand the earth's ionosphere. After about 20,000 years a magnetar will go quiet, but while it's active, the magnetic field has some incredible effects. From a few hundred thousand kilometers away, it would erase your credit card. From 1000 km away, you would be killed by the field tearing apart your tissues due to their high water content.

Basically, if you were to fall towards a neutron star, you would be torn apart by tidal forces, your remains would impact the surface at half the speed of light, and they would instantly be crushed and burned away. I'd say that's a top contender for Scariest Goddamn Thing in the Known Universe.