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Quasar Host Galaxies
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Hubble Space Telescope image courtesy of STScI

Quasi Stellar Objects: Quasars and Active Galaxies

Quasars, or quasi stellar objects, are so named because they are point-like objects just like stars. However, they are nothing like stars when they are analyzed. From spectroscopic analysis they are determined to be very distant, some are the most distant objects that we can see. But they are also very bright. Such intensity seen by Earth at such great distances indicates immensely high luminosity. What could they be? For many years Astronomers were baffled.

It has now been determined that Quasars are most likely the centers of Active Galaxies. In the center of many galaxies there may rest supermassive Black Holes. Around these Black Holes gigantic discs of matter falling onto them form. This matter is heated to unimaginably high temperatures and hence shines so bright that some Active Galactic Nuclei outshine their host galaxies.

In addition to the discs of infalling matter the Black Holes also form jets of matter that shoot out from the center of the galaxy. These jets can shoot out for Millions of Light-Years.

In this view quasars are special Active Galactic Nuclei that have their jets lined up with our line of sight. So we are looking straight down the jet and it seems extraordinarily bright.

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The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

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