Quasi Stellar Objects: Quasars and Active Galaxies



Quasar Host Galaxies
Click on image for full size (163K GIF)
Hubble Space Telescope image courtesy of STScI
Quasars, or quasi stellar objects, are named that way because they are star-like in appearance. But they are nothing like stars. They are very distant, some are the most distant objects that we can see. They are also very bright. What could they be? For many years Astronomers did not know.

Astronomers now think that Quasars are the centers of Active Galaxies. In the center of many galaxies there may rest supermassive Black Holes. Around these Black Holes gigantic discs of material fall on them. This material is heated to incredibly high temperatures and that makes them very bright. Some Quasars outshine their host galaxies.

The Black Holes also form jets of matter that shoot out from the center of the galaxy. When the galaxy is aligned so that we look straight down the jet we see a Quasar.

Quasi Stellar Objects: Quasars and Active Galaxies



Quasar Host Galaxies
Click on image for full size (163K GIF)
Hubble Space Telescope image courtesy of STScI
Quasars, or quasi stellar objects, are named that way because they are point-like objects just like stars. However, they are nothing like stars. From 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 that they are very energetic. 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.

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. 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.

Quasi Stellar Objects: Quasars and Active Galaxies



Quasar Host Galaxies
Click on image for full size (163K GIF)
Hubble Space Telescope image courtesy of STScI
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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