Neutronitäht

Neutronitäht, known in English as a neutron star, is an extremely dense stellar remnant formed after the supernova explosion of a massive star that had exhausted its nuclear fuel. When the core collapse halts due to neutron degeneracy pressure, the resulting object consists primarily of neutrons packed at nuclear densities, typically around 4×10^17 to 6×10^17 kilograms per cubic metre. A neutronitäht has a mass ranging from about 1.1 to 2.5 times the mass of the Sun, confined within a radius of only about 10 to 14 kilometres. This extreme compression yields gravitational fields so strong that spacetime curvature near the surface is significant, an effect exploited in tests of general relativity.

The formation of a neutronitäht occurs in stars between approximately 8 and 25 solar masses, though the exact mass range depends on metallicity and rotation. After the core is ejected, the remaining core collapses, and neutrino emission carries away most of the gravitational binding energy. The resulting object may exhibit rapid rotation, often with periods from milliseconds to seconds. Some neutronitas are observed as pulsars, emitting regular beams of radio waves; others are detected in X‑ray or gamma‑ray bands, often as X‑ray binaries or magnetars when magnetic fields exceed 10^10 tesla.

Observationally, neutron stars are studied through timing, spectra, and gravitational wave signatures. They provide laboratories for physics under extreme conditions, including tests of dense matter equations of state and nuclear interactions. The recent detection of binary neutron star mergers has opened the field of multimessenger astronomy, linking gravitational waves with electromagnetic counterparts and nucleosynthesis of heavy elements.