Thursday, June 20, 2019
Quasar and its Types:
Quasars, short for "quasi-stellar radio sources," are extremely luminous and energetic objects found at the centers of galaxies. They are powered by the accretion of mass onto supermassive black holes. Quasars emit large amounts of energy across the electromagnetic spectrum, making them detectable across vast cosmic distances.
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| QUASAR AND ITS TYPES |
There are several types of quasars based on their characteristics and observed properties:
1. Classical Quasars:
Classical quasars are the most well-known type. They are characterized by their extremely high luminosity, often outshining entire galaxies.
These quasars emit energy across a broad range of wavelengths, from radio waves to gamma rays.
Classical quasars are associated with the active galactic nuclei (AGN) of galaxies.
2. Blazars:
Blazars are a subcategory of quasars with jets of particles emitted at nearly the speed of light, directed towards Earth.
The emission from blazars is highly variable and can include gamma-ray, X-ray, and radio emissions.
Blazars are believed to be oriented in such a way that their jets are aligned with our line of sight, making them appear exceptionally bright.
3. Radio-Loud and Radio-Quiet Quasars:
Quasars are often classified based on their radio emission characteristics.
Radio-loud quasars have strong radio emissions, indicating the presence of powerful jets.
Radio-quiet quasars have weaker or no detectable radio emissions.
4. Optically Violently Variable (OVV) Quasars:
OVV quasars exhibit rapid and unpredictable variations in their optical brightness.
These variations can occur over timescales as short as a few days, suggesting highly dynamic processes in the vicinity of the supermassive black hole.
5. Narrow-Line Seyfert 1 Galaxies (NLS1):
NLS1 galaxies share some characteristics with quasars but have narrower emission lines in their spectra.
They are thought to be less massive than typical quasars and may represent a lower-luminosity counterpart.
6. Type 2 Quasars:
Type 2 quasars exhibit broad emission lines in their spectra, similar to classical quasars, but they also show features indicative of obscured or blocked central regions.
This suggests the presence of dense material (such as gas and dust) that partially obscures our view of the central supermassive black hole.
The study of quasars has provided valuable insights into the nature of active galactic nuclei, the behavior of supermassive black holes, and the processes occurring in the early universe. The diversity of quasar types reflects the variety of physical conditions and orientations observed in these highly energetic systems.