ASTROPHYSICS (Greek ’αστρον [astron]—start; φυσικος [physikos]—concerning studies of nature)—a science that applies physical methods of investigation to astronomical objects (stars, star clusters, galaxies, quasars, and pulsars).
Astrophysics began in the late nineteenth century and developed intensely in the twentieth century. The use of increasingly large telescopes enabled astronomers to identify objects at increasingly great distances from Earth. Telescopes equipped with cameras allowed them to photograph these objects, and by attaching spectrographs they could obtain the spectra of the objects. By using photometers (and photographic duplicators) they could measure the relative intensity of radiation in different parts of the spectrum. They could use polarization meters to determine the degree of polarization of this radiation. After the Second World War, astrophysicists began to use radio waves, x-rays, and gamma rays.
Astrophysical research allowed scientists to identify several objects unknown to classical astronomy (neutron stars, quasars, etc.) and provided data on the chemical composition and physical properties (density, temperature, and age) of stars, star clusters, galaxies, and interstellar matter. On the basis of this data, scientists formulated procedures to classify objects (spectral classes of stars, clusters, etc.) and established various laws (the Hertzsprung-Russell diagram, Hubble’s law). The findings of astrophysics provide material for cosmological models of the universe.
W. Zonn, Astrofizyka ogólna [General astrophysics], Wwa 1955; J. S. Stodółkiewicz, Astrofizyka ogólna z elementami geofizyki [General astrophysics with elements of geophysics], Wwa 1971, 19824; M. Ryan, L. Shepley, Homogeneous Relativistic Cosmologies, Pri 1975; M. Demiański, Astrofizyka relatywistyczna [Relativistic astrophysics], Wwa 1978, 19912.