Active nucleus - with a relativistic jet that is pointed in...

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Active nucleus A portion of the galaxies we can observe are classified as active. That is, a significant portion of the total energy output from the galaxy is emitted by a source other than the stars, dust and interstellar medium . The standard model for an active galactic nucleus is based upon an accretion disc that forms around a supermassive black hole (SMBH) at the core region. The radiation from an active galactic nucleus results from the gravitational energy of matter as it falls toward the black hole from the disc. [75] In about 10% of these objects, a diametrically opposed pair of energetic jets ejects particles from the core at velocities close to the speed of light . The mechanism for producing these jets is still not well understood. [76] A jet of particles is being emitted from the core of the elliptical radio galaxy M87 . Active galaxies that emit high-energy radiation in the form of x-rays are classified as Seyfert galaxies or quasars , depending on the luminosity. Blazars are believed to be an active galaxy
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Unformatted text preview: with a relativistic jet that is pointed in the direction of the Earth. A radio galaxy emits radio frequencies from relativistic jets. A unified model of these types of active galaxies explains their differences based on the viewing angle of the observer. [76] Possibly related to active galactic nuclei (as well as starburst regions) are low-ionization nuclear emission-line regions (LINERs). The emission from LINER-type galaxies is dominated by weakly ionized elements. [77] Approximately one-third of nearby galaxies are classified as containing LINER nuclei. [75] [77] [78] [ edit ] Formation and evolution Main article: Galaxy formation and evolution The study of galactic formation and evolution attempts to answer questions regarding how galaxies formed and their evolutionary path over the history of the universe. Some theories in this field have now become widely accepted, but it is still an active area in astrophysics ....
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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