The Quasar

Quasar is the deadliest object in the universe (long post) A quasar is a type of object in the universe that is characterized by a sufficiently high luminosity and such a small angular size that for several years after their discovery they could not be distinguished from "point sources" – stars. According to modern concepts, quasars are active galactic nuclei at the initial stage of development, in which a supermassive black hole absorbs the surrounding matter, forming an accretion disk. Quasars were discovered as objects with a large redshift, having electromagnetic radiation (including radio waves and visible light) and such small angular sizes that for several years after their discovery they could not be distinguished from "point sources" — stars (on the contrary, extended sources correspond more to galaxies; the magnitude of the brightest quasar is +12.6). Traces of parent galaxies around quasars (and not all of them) they were discovered only later.

Quasars are detected over a very wide range of distances, and research on quasar detection has shown that quasar activity was more widespread in the distant past. The peak of the era of quasar activity was about 10 billion years ago.

Quasars are called beacons of the universe. They are visible from great distances (up to a redshift exceeding z = 7.5), they study the structure and evolution of the Universe, determine the distribution of matter on the line of sight: strong spectral absorption lines of hydrogen unfold into a forest of lines along the redshift of absorbing clouds. Due to their great distance, quasars, unlike stars, look almost stationary (they do not have parallax), so the radio emission from the quasar is used to accurately determine the trajectory parameters of an automatic interplanetary station from Earth.

As of the end of 2023, the most distant detected quasar is redshifted UHZ1. The light observed from this quasar was emitted when the universe was 470 million years old.