Formation of neutron stars and black holes
Pro Research Analysisby 
Searched over 200M research papers
Formation of Neutron Stars and Black Holes: Stellar Evolution and Core Collapse
Neutron stars and black holes are the compact remnants left behind after the life cycles of massive stars. When a massive star exhausts its nuclear fuel, its core collapses under gravity. If the remaining core mass is below a certain threshold, it forms a neutron star; if it exceeds this threshold, a black hole is created. These objects are so dense that Newtonian gravity cannot describe the forces near their surfaces, requiring general relativity for accurate modeling .
Binary Neutron Star Mergers and Black Hole Formation
Mergers of binary neutron stars are a key pathway for black hole formation. When two neutron stars spiral together and merge, the outcome depends on the total mass and the equation of state (EOS) of nuclear matter. If the combined mass exceeds a critical threshold, a prompt collapse to a black hole occurs. This threshold is influenced by the mass ratio, the intrinsic spin of the neutron stars, and the stiffness of the EOS Shibata2006Kiuchi2009Bernuzzi2020+3 MORE. Simulations show that for high-mass systems, black holes form rapidly after the merger, often surrounded by a disk of neutron-rich material and accompanied by the emission of gravitational waves and electromagnetic signals such as kilonovae Shibata2006Kiuchi2009Bernuzzi2020+3 MORE.
Influence of Spin and Mass Ratio on Black Hole Formation
The spin of neutron stars in a binary system can significantly affect the merger outcome. Higher spins increase the threshold mass required for prompt black hole formation, and the orientation of the spins relative to the orbital motion can change the dynamics of the merger, the mass of the debris disk, and the gravitational wave signal Helbich2023Schianchi2024. High mass ratios (where one star is much more massive than the other) can also lead to prompt black hole formation, with more massive accretion disks and brighter electromagnetic counterparts .
Alternative Formation Channels: Core Collapse and Exotic Scenarios
Besides binary mergers, isolated massive stars can undergo core collapse, leading to the formation of neutron stars or black holes. In some modified gravity theories, such as scalar-Gauss-Bonnet gravity, the collapse can produce "scalarized" neutron stars or black holes, which may have unique observational signatures . Additionally, there are theoretical scenarios where neutron stars could collapse into black holes through the accumulation of dark matter in their cores, especially in models involving bosonic dark matter .
Black Hole–Neutron Star Binaries and Dynamical Formation
Black hole–neutron star (BHNS) binaries can form through both isolated binary evolution and dynamical interactions in young star clusters. Dynamically formed BHNS systems tend to be more massive than those formed in isolation, and their mergers can provide clues about their origin based on the observed mass spectrum in gravitational wave detections .
Conclusion
The formation of neutron stars and black holes is governed by the mass and properties of the progenitor star or binary system, the equation of state of nuclear matter, and additional factors like spin and mass ratio. Binary neutron star mergers are a major channel for black hole formation, with outcomes that can be probed through gravitational waves and electromagnetic signals. Alternative scenarios, including those involving modified gravity or dark matter, offer additional pathways and potential observational signatures. Understanding these processes is crucial for interpreting observations and advancing our knowledge of fundamental physics and astrophysics Maccarone2013Kuan2021Shibata2006+7 MORE.
Sources and full results
Most relevant research papers on this topic