Quasar, definition and study of Cognitio.

A quasar is an extremely bright active galactic nucleus and generally very far from Earth (of the billions of light years). The name derives from the fact that these objects, whose nature was controversial until the early eighties, were initially discovered as powerful radio sources, whose optical counterpart was as point-sticks as a star. The great shift towards the red quasar character, according to Hubble’s law, implies that they are far distant objects and that therefore they must emit energy equivalent to hundreds of normal galaxies

Galaxy, definition and study. A-Z index of Cognitio.


It is commonly believed that such great luminosity originates from the frustration caused by gases and dust falling into a black super-massive hole; they form an augmentation disk that converts about half the mass of an object into energy.

Black hole, definition and study. A-Z index of Cognitio.

Black hole

Despite these tremendous brightness, the size of the quasar is comparable to that of the solar system, but no bigger than a few light years.

Solar system, definition and study. A-Z Index of Cognitio.

Solar system

These dimensions are estimated by virtue of the fact that the brightness of the quasars is highly variable and with a rather short period of time a few hours to a few months and considering that from a relativistic point of view, an object can not change brightness faster than the time it takes to pass through it. The other characteristic aspect, apparent from the earliest observations, is that the quasars have a vast spectrum across all frequencies, gamma rays, X-rays to far-infrared, and for 10% of quasars known up to radio frequencies .

Astronomical observation, definition and study. A-Z index of Cognitio.

Astronomical observation

The images of the Hubble Space Telescope of various quasars allowed in the nineties to discover the galaxies hosted by these objects, thus providing decisive evidence for framing these objects in the unified models of active galaxies. 3C 273 is one of the quasars closest to us and the brightest known; is also one of the most studied, especially for the complex structure of high-speed ejected gas jet, extending into space for 150,000 light years, highlighted by Chandra and Hubble satellites. Located at 3 billion light years, it is brighter than 1000 galaxies containing 100 billion stars each; if it were at 32-year light distance from Earth, it would illuminate the sky as much as the Sun.

Sun, definition and study. A-Z index of Cognitio.


By observing this object throughout the electromagnetic spectrum, one begins to understand the nature of the physical processes underlying these enormous energy sources.

Quasar, definition and study of Cognitio.



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Quasar, definition and study of Cognitio.