It is theorized that neutron stars are the collapsed cores of massive suns. If you imagine a collapsed version of the Earth’s sun, this sun would punch itself down into a ball that could cover the city of Chicago. This video by FabioTheItalianOne is a wonderful way to understand massive stars by comparing Earth and the Sun to massive stars like Antares and Arcturus.
What type of star becomes a neutron star?
Stars or suns eventually run out of fuel, which triggers a collapse. But not just any star will become a neutron star. Here is a list of expectations, based on the original size of the collapsing star:
Stars that are less than 8 times the size of the sun tend to become white dwarfs.
Stars that have from 8 to 30 times the mass of the sun are most likely to become neutron stars.
Stars that are over 30 times more massive than the sun tend to become black holes.
The initial formation of a neutron star is a dramatic process.
The collapsing star that meets the standard for a neutron star will develop density so powerful that the protons and electrons squeeze tightly enough together to form neutrons. At this point, all of the original weight of the star is now smashed into a vastly smaller mass that is made up mostly of neutrons.
Extremely strong gravitational and magnetic fields surround the much smaller new mass. The neutron star then becomes one of the most rapidly rotating masses in space, rotating at something like 700 times per second.
To give an idea of the mass of of neutron stars, there are many common estimates that compare a piece of the neutron star to objects that humans recognize. A piece the size of a grain of sand could weigh 4 million tons. A baseball sized piece might weigh 50 trillion pounds.
This is not the end of the formation or changes that the star will go through! Neutron stars either continue to develop into an amazing array of sub types, or they can go through yet to be discovered events that will present an endless universe of surprises.
Pulsars, Magnetar Pulsars and Starquakes
Wikipedia lists 18 sub types of neutron stars, a few of which are entirely hypothetical and based on ideas of what could be happening out in space. Two familiar types of neutron stars are pulsars and magnetars.
As the neutron star spins, it can turn into a giant electrical generator and starts to spray out pulses of highly radioactive and deadly particles. This is how a neutron star becomes a “pulsar”. Sometimes the particles form a cloud that is called a “pulsar wind nebula” which is detected as x-rays.
Magnetars are neutron stars that develop incredible magnetic fields with about a quadrillion times the power of Earth’s magnetic field.
Starquakes occur when the powerful magnetic fields attack and create fractures to the star’s own structure.
For an excellent and detailed discussion of Neutron stars, Professor M Coleman Miller of the University of Maryland has a web page titled “Introduction To Neutron Stars”.