Fan, Xiaohui Steward Observatory, The University of Arizona, Tucson, Arizona.
Last reviewed:February 2019
Show previous versions
- General characteristics
- Very small angular size
- High luminosity
- Broadband continuum emission
- Strong and broad emission lines
- Surveys of quasars
- Quasar model and energy source
- Quasars and cosmology
- Related Primary Literature
- Additional Reading
An astronomical object that appears starlike on ground-based images but possesses many other characteristics, such as a large redshift, that prove it is not a star. Quasars are the most luminous members of a larger family of objects referred to as active galactic nuclei (AGNs). Found at the centers of galaxies, quasars often outshine their galactic host by a factor of 100–1000, making them among the most luminous and energetic sources in the universe. Because of their high luminosity, quasars can be detected at great distances, and are therefore also among the most distant objects ever observed. Astronomers widely believe that the accretion of hot gas into supermassive black holes at galactic centers provides the energy that powers quasars (Fig. 1). Quasars are useful probes of cosmology, the formation of black holes, and the evolution of galaxies in the universe. See also: Black hole; Cosmology; Galaxy; Supermassive black hole; Universe
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information