Neutronitähdistä

Neutronitähdistä, known in English as a neutron star, is an extremely dense remnant of a massive star that has ended its life in a core‑collapse supernova. When a star of roughly 8 to 20 solar masses exhausts its nuclear fuel, its iron core can no longer support itself against gravitational collapse. The core implodes, and if the resulting density exceeds about 10^18 kilograms per cubic meter, protons and electrons combine to form neutrons, creating a neutron‑rich sphere composed almost entirely of neutrons.

The structure of a neutronitähdistä is layered: a solid crust of neutron‑rich nuclei encloses a fluid interior that may contain superfluid neutrons and a superconducting proton component. The star’s surface magnetic field is typically on the order of 10^8 to 10^15 gauss, far stronger than Earth's field, and the magnetic axis can be misaligned with the rotation axis, giving rise to pulsar emission.

Rotation periods range from milliseconds to several seconds. Millisecond pulsars, often found in binary systems, have been spun up by accreting matter from a companion. Ordinary pulsars spin down over time due to magnetic dipole radiation and particle wind losses. The intense gravitational field also warps spacetime, producing gravitational waves during asymmetric events such as starquakes or binary mergers.

Neutronitähdistä are observable through radio, optical, X‑ray, and gamma‑ray emission. Their discovery has provided insights into quantum chromodynamics at extreme densities, nuclear equation of state, and the behavior of matter under gravitational fields billions of times stronger than those achievable on Earth. The study of these objects continues to bridge astrophysics, nuclear physics, and relativity.