Neutron stars: compact objects with relativistic gravity


Ekşi K. Y.

TURKISH JOURNAL OF PHYSICS, cilt.40, sa.2, ss.127-138, 2016 (ESCI) identifier identifier

  • Yayın Türü: Makale / Derleme
  • Cilt numarası: 40 Sayı: 2
  • Basım Tarihi: 2016
  • Doi Numarası: 10.3906/fiz-1510-11
  • Dergi Adı: TURKISH JOURNAL OF PHYSICS
  • Derginin Tarandığı İndeksler: Emerging Sources Citation Index (ESCI), Scopus, TR DİZİN (ULAKBİM)
  • Sayfa Sayıları: ss.127-138
  • Anahtar Kelimeler: Neutron stars, gravity, general relativity, EQUATION-OF-STATE, SOFT GAMMA-REPEATERS, X-RAY BINARIES, DENSE MATTER, MAXIMUM MASS, MILLISECOND PULSARS, GENERAL-RELATIVITY, NUCLEAR-EQUATION, MAGNETIC-FIELDS, RECENT PROGRESS
  • İstanbul Teknik Üniversitesi Adresli: Evet

Özet

General properties of neutron stars are briefly reviewed with an emphasis on the indispensability of general relativity in our understanding of these fascinating objects. In Newtonian gravity the pressure within a star merely plays the role of opposing self-gravity. In general relativity all sources of energy and momentum contribute to the gravity. As a result, the pressure not only opposes gravity but also enhances it. The latter role of pressure becomes more pronounced with increasing compactness, M/R, where M and R are the mass and radius of the star, and sets a critical mass beyond which collapse is inevitable. This critical mass has no Newtonian analogue; it is conceptually different from the Chandrasekhar limit in Newtonian gravity, which is attained asymptotically for ultra-relativistic fermions. For white dwarfs the general relativistic critical mass is very close to the Chandrasekhar limit. For neutron stars the maximum mass so called Oppenheimer-Volkoff limit is significantly smaller than the Chandrasekhar limit. This follows from the fact that the general relativistic correction to hydrostatic equilibrium within a neutron star is significant throughout the star, including the central part, where the mass contained within the radial coordinate, m(r), and the Newtonian gravitational acceleration, Gm(r)/r(2), is small.