Seyfert galaxy

Seyfert galaxy
/suy"feuhrt, see"-/, Astron.
one of a group of spiral galaxies with compact, bright nuclei having characteristically broad emission lines suggestive of very hot gases in violent motion at the center.
[1965-70; named after Carl K. Seyfert (1911-60), American astronomer, who first described them]

* * *

 any of a class of galaxies (galaxy) known to have active nuclei. Such galaxies were named for the American astronomer Carl K. Seyfert, who first called attention to them in 1944. Two types are recognized. The nuclear spectra of Type 1 Seyfert galaxies show broad emission lines, which are indicative of a central concentration of hot gas that is expanding at speeds of up to thousands of kilometres per second. Type 2 Seyferts have strong emission lines, but they indicate more-modest velocities, less than 1,000 km/sec. Seyfert galaxies appear normal in ordinary images but are extremely strong sources of infrared radiation. Moreover, many are powerful sources of radio energy and X-rays (X-ray) as well. Seyfert nuclei are related to quasars (quasar) but apparently involve smaller amounts of energy release. Like quasars, they are thought to be powered by massive black holes (black hole) at their centres. About 1 percent of all spiral galaxies are thought to exhibit Seyfert properties, or perhaps all spiral galaxies are Seyferts 1 percent of the time.

Paul W. Hodge

* * *

Universalium. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Seyfert galaxy — ☆ Seyfert galaxy [sē′fərt ] n. [after Carl K. Seyfert, U.S. astronomer who discovered them in the 1940s] any of a number of spiral galaxies with a small, intensely bright nucleus and a spectrum with strong, broad spectral lines …   English World dictionary

  • Seyfert galaxy — Seyfert galaxies are a class of galaxies with nuclei that produce spectral line emission from highly ionized gascite book author=L. S. Sparke, J. S. Gallagher III year=2007 title=Galaxies in the Universe: An Introduction publisher=Cambridge… …   Wikipedia

  • Seyfert galaxy — [ seɪfə:t] noun Astronomy a galaxy of a type characterized by a bright compact core showing strong infrared emission. Origin 1950s: named after the American astronomer Carl K. Seyfert …   English new terms dictionary

  • Seyfert galaxy — noun Etymology: Carl K. Seyfert died 1960 American astronomer Date: 1959 any of a class of spiral galaxies that have small compact bright nuclei characterized by variability in light intensity, emission of radio waves, and spectra called also… …   New Collegiate Dictionary

  • seyfert galaxy — ¦sēfə(r)t , ¦sī noun or seyfert ( s) Usage: usually capitalized S Etymology: after Carl K. Seyfert died 1960 American astronomer : any of a class of spiral galaxies that have small compact bright nuclei exhibiting variability in light intensity,… …   Useful english dictionary

  • Seyfert galaxy — /ˈsaɪfət/ (say suyfuht) noun one of a number of galaxies with very bright nuclei. {named after Carl K Seyfert, US astronomer} …   Australian-English dictionary

  • Seyfert Galaxy —    Any of a class of spiral galaxies with a small, yet very active, nucleus. See Active Galactic Nucleus …   The writer's dictionary of science fiction, fantasy, horror and mythology

  • Galaxy groups and clusters — are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation.[1] They form the densest part of the large scale structure of the universe. In models for the gravitational formation of… …   Wikipedia

  • galaxy — /gal euhk see/, n., pl. galaxies. 1. Astron. a. a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space. b. (usually cap.) See Milky Way. 2. any large and brilliant or impressive… …   Universalium

  • Galaxy — This article is about the astronomical structure. For other uses, see Galaxy (disambiguation). NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 55,000 light years in diameter and approximately 60 million light… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”