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Active galactic nucleus

Active galactic nucleus

Compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion – and possibly all – of the electromagnetic spectrum

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Edits on 24 Jun, 2020
Neelam Jhaveri
Neelam Jhaveri approved a suggestion from Golden's AI on 24 Jun, 2020
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Most, if not all, normal galaxies have a supermassive black hole at their center. In an active galaxy, its supermassive black hole is accreting material from the galaxy's dense central region. As the material falls in toward the black hole, angular momentum will cause it to spiral in and form into a disk. This disk, called an accretion diskaccretion disk, heats up due to the gravitational and frictional forces at work.

Neelam Jhaveri
Neelam Jhaveri approved a suggestion from Golden's AI on 24 Jun, 2020
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Most, if not all, normal galaxies have a supermassive black holesupermassive black hole at their center. In an active galaxy, its supermassive black hole is accreting material from the galaxy's dense central region. As the material falls in toward the black hole, angular momentum will cause it to spiral in and form into a disk. This disk, called an accretion disk, heats up due to the gravitational and frictional forces at work.

Edits on 22 Jun, 2020
Jude Gomila
Jude Gomila approved a suggestion from Golden's AI on 22 Jun, 2020
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Models of active galaxies also include a region of cold gas and dust, thought to be in the shape of a giant donut with the black hole and accretion disk nestled in the donut's hole. In about one out of ten AGN, the black hole and accretion disk produce narrow beams of energetic particles and ejects them outward in opposite directions away from the disk. These jets, which emerge at nearly the speed of light, become a powerful source of radio waveradio wave emission.

Edits on 21 Jun, 2020
Christopher Agostino
Christopher Agostino edited on 21 Jun, 2020
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Active galaxies are galaxies that have a small core of emission embedded at the center of an otherwise typical galaxy. This core is typically highly variable and very bright compared to the rest of the galaxy.

For normal galaxies, we think of the total energy they emit as the sum of the emission from each of the stars found in the galaxy, but in active galaxies, this is not true. There is a great deal more emitted energy in active galaxies than there should be and this excess energy is found in the infrared, radio, UV, and X-ray regions of the electromagnetic spectrum. The energy emitted by an active galaxy, AGN for short, is anything but normal. So what is happening in these galaxies to produce such an energetic output?

Most, if not all, normal galaxies have a supermassive black hole at their center. In an active galaxy, its supermassive black hole is accreting material from the galaxy's dense central region. As the material falls in toward the black hole, angular momentum will cause it to spiral in and form into a disk. This disk, called an accretion disk, heats up due to the gravitational and frictional forces at work.

Models of active galaxies also include a region of cold gas and dust, thought to be in the shape of a giant donut with the black hole and accretion disk nestled in the donut's hole. In about one out of ten AGN, the black hole and accretion disk produce narrow beams of energetic particles and ejects them outward in opposite directions away from the disk. These jets, which emerge at nearly the speed of light, become a powerful source of radio wave emission.

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The properties of an active galaxy are determined by the black hole's mass, the rate of accretion onto the black hole, whether or not it has a powerful jet, and the angle at which we view the galaxy. Radio galaxies, quasars, and blazars are AGN with strong jets that can travel outward into large regions of intergalactic space. Some of the apparent differences between types of AGN are due to our having different orientations with respect to the disk. With blazars and quasars, we are looking down the jet.

Edits on 23 Apr, 2020
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Golden AI edited on 23 Apr, 2020
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Edits on 1 Jan, 2017
Golden AI"Initial topic creation"
Golden AI created this topic on 1 Jan, 2017
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 Active galactic nucleus

Compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion – and possibly all – of the electromagnetic spectrum

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