????Learn Astronomy in the largest Astronomy Course in Brazil: https://academyspace.com.br/bigbang To understand what a neutron star is, we first need to understand the life cycle of massive stars. For now, let's forget about stars with a mass equivalent to the mass of the Sun. Here, we'll talk about stars that have a mass between 8 and 20 times the mass of the Sun. These stars live less and quickly become red supergiants. After countless processes of contraction and expansion, the red supergiant explodes in what we call a supernova, one of the most important events in the universe, and an event that represents the end of the life of a massive star. However, the life of the star does not end there. After the explosion, a stellar core remains, and this core can have basically two fates. If what remains has between 1.5 and 3 times the mass of the Sun, this core transforms into a so-called neutron star. If this remaining core has more than 3 times the mass of the Sun, it becomes a black hole. Both neutron stars and black holes are classified in astrophysics as compact objects. In short, a neutron star is small in size, tens of kilometers in diameter, but has a mass much greater than the Sun, 3 times, for example, that is, its density is very high. This makes neutron stars the smallest and most massive stars known. They are given this name because the stellar core that remained from the supernova explosion is nothing more than a superfluid of neutrons, it is like a paste of neutrons. In fact, the structure of a neutron star is not very well known, because these conditions cannot be reproduced in the laboratory. Neutron stars emit a lot of radiation in the X-ray wavelength and little radiation in the visible light wavelength, so their detection is not easy. If this neutron star starts to spin rapidly, it generates violent magnetic fields through which jets of radiation escape. This rapidly rotating neutron star is called a pulsar, and emits most of its radiation in the radio wavelength range. The event known as GW170817 resulted from the merger of two neutron stars, one with masses between 1.17 and 1.60 times that of the Sun, resulting in a final object with 2.74 times the mass of the Sun. Astronomers have known about pulsars for more than 50 years, which are a source of radio waves in the universe, but they did not yet know where the gamma-ray bursts they observed were coming from. This event served to show that the merger of neutron stars generates a rapid burst of gamma rays. Furthermore, astronomers already knew that elements heavier than iron were forged in the cores of neutron stars, and this was also proven when, during the merger of two neutron stars, large quantities of elements such as uranium, gold, and platinum were thrown into space. The history of neutron stars is much more complex than what I have mentioned here. I will leave a series of links in the description, including presentations of astronomy courses around the world where a historical review of how this definition was reached and more in-depth details about the characteristics of neutron stars are provided. Sources: https://www.jlab.org/conferences/PREX... http://www-astro.ulb.ac.be/~chamel/do... http://www.astro.ufl.edu/~eiken/AST79... https://theconversation.com/explainer...