Neutron star

Moving heart of the Crab Nebula

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Neutron star cross section

Neutron Star

A neutron star is a type of compact star that is the remnant of a massive star after it has undergone a supernova explosion. It is composed almost entirely of neutrons, subatomic particles with no net electric charge and slightly larger mass than protons. Neutron stars are incredibly dense, with masses comparable to that of the Sun, but with radii of only about 10 kilometers (6 miles), leading to densities billions of times greater than that of any material on Earth. The concept of neutron stars was first proposed by Walter Baade and Fritz Zwicky in 1934, shortly after the discovery of the neutron by James Chadwick.

Formation

Neutron stars are formed when the core of a massive star collapses under the force of gravity during a supernova explosion. This collapse continues until the densities become so high that protons and electrons combine to form neutrons and neutrinos in a process known as neutronization. The newly formed neutron star then cools and stabilizes, emitting a burst of neutrinos.

Characteristics

Neutron stars possess extremely strong magnetic fields, billions of times stronger than Earth's magnetic field. These magnetic fields, along with the rapid rotation rates of neutron stars, can lead to the emission of intense electromagnetic radiation, particularly in the form of X-rays and gamma rays. When these emissions are observed, the neutron star is often referred to as a pulsar or a magnetar, depending on the characteristics of the emissions.

Pulsars

Pulsars are neutron stars that emit beams of radiation that sweep through Earth's line of sight, producing a pulsed signal that can be detected by radio telescopes. The first pulsar was discovered in 1967 by Jocelyn Bell Burnell and Antony Hewish, marking a significant milestone in the study of neutron stars.

Magnetars

Magnetars are a type of neutron star with extremely powerful magnetic fields, thousands of times stronger than those of typical pulsars. Magnetars are responsible for emitting intense bursts of X-rays and gamma rays, phenomena known as soft gamma repeaters and anomalous X-ray pulsars.

Significance in Astrophysics

Neutron stars provide a unique environment for the study of matter under extreme conditions. They are laboratories for nuclear physics, quantum mechanics, and general relativity. The study of neutron stars can offer insights into the behavior of matter at nuclear densities, the nature of gravitational waves, and the properties of neutron-rich matter, which is relevant for understanding nuclear fusion processes in stars.

See Also

• Black hole
• White dwarf
• Stellar evolution
• Supernova remnant