Neutron stars are incredibly dense objects that form when a massive star undergoes a supernova explosion and its core collapses. The mass of a neutron star can range from about 1.1 to 3 times the mass of the Sun, with typical neutron stars falling within the range of 1.4 to 2.1 solar masses. These values are estimates based on observational data and theoretical models.
It's worth noting that there is an upper limit to the mass of a stable neutron star, beyond which it would likely collapse further into a black hole. This limit, known as the Tolman-Oppenheimer-Volkoff (TOV) limit, is estimated to be around 2 to 3 solar masses. However, the exact value depends on the properties of dense matter under extreme conditions, which are still not fully understood.
There have been several discoveries of neutron stars with masses close to the upper limit, such as the pulsar PSR J0740+6620, which has a mass of about 2.14 solar masses. These observations provide valuable insights into the physics of extremely dense matter and the behavior of matter under intense gravitational forces.