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How are quasars different from Seyfert galaxies?
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Quasar
Six quasar host galaxies, as observed by the Hubble Space Telescope.
Shown are apparently normal, solitary galaxies (left), colliding galaxies (centre), and merging galaxies (right).
Both quasars and Seyfert galaxies are types of active galactic nuclei (AGN) powered by matter accreting onto a central supermassive black hole. The primary difference between them lies in their level of energy output and luminosity.1234
- Luminosity: Quasars are extreme, highly luminous objects that can outshine all the stars in their host galaxy. In contrast, Seyfert galaxies exhibit lower-level activity, and their nuclei are less energetic than those of quasars.541
- Visibility: Because a quasar’s radiation is so intense, it often overwhelms the light from its host galaxy, making the galaxy difficult to detect without specialized techniques. Seyfert galaxies, however, appear as normal galaxies in standard images, with their active nuclei being a distinct feature within them.41
- Fueling Mechanisms: The difference in activity levels is believed to stem from the amount of fuel available to the central black hole. Quasar activity is often triggered by major events, such as an encounter with another galaxy that provides a large influx of matter, whereas the activity in Seyfert nuclei involves smaller amounts of captured mass.4