Neutron stars

Neutron Star

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Object type	Stellar remnant
Other designations
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A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a supernova event. Neutron stars are the smallest and densest stars known, excluding black holes, hypothetical quark stars, and other speculative dense stellar objects. They typically have a radius on the order of 10 kilometers and a mass about 1.4 to 2.16 times that of the Sun, which corresponds to the Tolman–Oppenheimer–Volkoff limit, the maximum mass a neutron star can achieve before collapsing into a black hole.

Characteristics

Neutron stars are composed almost entirely of neutrons, which are subatomic particles with no net electric charge and slightly larger mass than protons. The extreme density of neutron stars is such that a sugar-cube-sized amount of neutron star material would have a mass of about 100 million tons on Earth. The surface of a neutron star is expected to be composed of degenerate matter, with a crust of iron nuclei and electrons.

Formation

Neutron stars are formed when the core of a massive star undergoes gravitational collapse, leading to a supernova explosion. The core is compressed to such an extent that protons and electrons combine to form neutrons and neutrinos in a process known as neutronization. The newly formed neutron star is predominantly composed of neutrons.

Rotation and magnetic fields

Neutron stars are known for their rapid rotation rates and strong magnetic fields. These stars can spin at up to several hundred times per second. Some neutron stars, known as pulsars, emit beams of electromagnetic radiation from their magnetic poles. These beams are observable when they sweep across the Earth, appearing as regular pulses of radiation.

Types of neutron stars

There are several types of neutron stars, including:

• Pulsars - Neutron stars that emit beams of radiation that are observed as pulses.
• Magnetars - Neutron stars with extremely strong magnetic fields, which can lead to starquakes and gamma-ray flares.
• Radio-quiet neutron stars - Neutron stars that do not emit strong beams of radiation, making them detectable primarily through their gravitational influence.

Scientific significance

Neutron stars are of great interest to astronomers and physicists because they provide a natural laboratory for studying the properties of matter under extreme conditions. The study of neutron stars can help scientists understand the fundamental aspects of physics, including the behavior of matter at nuclear densities and the effects of extremely strong gravitational and magnetic fields.

See also

• Black hole
• White dwarf
• Stellar evolution
• Compact star