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An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. This energy, depending on the active galaxy type, can be emitted across most of the electromagnetic spectrum, as infrared, radio waves, Ultra Violet, X-ray and gamma rays. NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant. ...
The Pleiades, an open cluster of stars in the constellation of Taurus. ...
The distribution of ionized hydrogen (known by astronomers as H II (aitch two) from old spectroscopic terminology) in the parts of the Galactic interstellar medium visible from the Earths northern hemisphere (from the Wisconsin H-Alpha Mapper Survey) In astronomy, the interstellar medium (or ISM) is the matter (interstellar...
Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency HF = High frequency...
Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...
Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ...
Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ...
In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...
This article is about electromagnetic radiation. ...
 A 5000 light-year (50 Em or 30,000,000,000,000,000 mile) long jet is ejected from active galaxy M87 (the yellow ball at top left). Electrons are ejected outward at near light-speed, emitting eerie blue light. Frequently, the abbreviation AGN (Active Galactic Nuclei) is used, since most active galaxies appear to be powered by a compact region in the galactic centre. Some of these compact regions emit jets of matter that can extend for very large distances, powering extended structures (such as radio galaxies and radio-loud quasars). But in all cases the active nucleus or central engine is the fundamental source of energy. Download high resolution version (611x638, 41 KB)from http://hubblesite. ...
Download high resolution version (611x638, 41 KB)from http://hubblesite. ...
The jet emitted by M87 in this image is thought to be caused by a supermassive black hole at the galaxys center. ...
Relativistic Jet. ...
An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ...
This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ...
The standard theoretical model is that the energy is generated by matter falling onto a supermassive black hole of between 106 and 1010 solar masses. As the material falls into the black hole, angular momentum causes the material to flatten into an accretion disk. Frictional heating causes the infalling material to turn into plasma and emit strongly in the optical, ultra-violet or X-ray bands. Frequently, one observes jets emanating from the accretion disk, although the mechanism of formation of those jets is poorly understood. The accretion mechanism is highly efficient at turning matter into energy, and can convert almost 50% of the mass-energy of an object into energy as compared with only a few percent with nuclear fusion. Supermassive Black Hole is the first single by the British rock band Muse from their forthcoming album, Black Holes And Revelations. ...
Gyroscope. ...
An accretion disc (or accretion disk) is a structure formed by material falling into a gravitational source. ...
A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation A solar coronal mass ejection blasts plasma throughout the solar system. ...
See also list of optical topics. ...
Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ...
In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...
The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...
It is believed that when the black hole has eaten all of the gas and dust in its neighborhood that the active galactic nucleus ceases to emit large amounts of radiation and becomes a normal galaxy. This model is supported by what appears to be a quiet supermassive black hole in the center of the Milky Way, and in other nearby galaxies, and also nicely explains why quasars appear to have been much more common in the early universe, when more fuel was available. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias), sometimes referred to simply as the Galaxy), is a barred spiral galaxy which forms part of the Local Group. ...
This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ...
This model also explains the different types of active galactic nuclei, which are believed to all be due to the same type of source, but can appear quite different depending on the angle the source makes to the earth, and the amount of gas and dust available to be fed into the black hole.
Types of active galaxies
Seyferts, quasars and blazars are the main types of AGNs that emit high-energy radiation (X-rays), although all AGNs emit X-rays to some extent. Quasars, in particular, are thought to be the most consistently luminous objects in the known universe. Seyfert galaxies are spiral or irregular galaxies containing an extremely bright nucleus, most likely caused by a supermassive black hole, that can sometimes outshine the surrounding galaxy. ...
This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ...
A blazar is a very compact and highly variable energy source associated with a supermassive black hole at the center of a galaxy. ...
In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...
Radio galaxies are active galaxies with strong, extended radio emission, powered by relativistic jets from the active nucleus. An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ...
Relativistic Jet. ...
Some of the different types of active galaxy are linked by Unified models in which they are really the same class of object seen at different viewing angles, with relativistic beaming and dust obscuration causing the observational differences. The two main unified models link the different classes of Seyferts and radio galaxies, quasars and blazars. Seyfert galaxies are spiral or irregular galaxies containing an extremely bright nucleus, most likely caused by a supermassive black hole, that can sometimes outshine the surrounding galaxy. ...
An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ...
This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ...
A blazar is a very compact and highly variable energy source associated with a supermassive black hole at the center of a galaxy. ...
Optical Spectra Seyfert 1 spectra are characterized by broad and narrow emission lines. Quasar spectra are qualitatively similar to those of Seyfert 1s.
Example spectrum of a Seyfert 1 galaxy (SWIFT J0904.3+5538) with broad emission lines clearly visible. Seyfert 2 spectra are characterized by narrow emission lines. Their polarized spectra may also show broad lines. Image File history File links Download high-resolution version (850x680, 15 KB)Sloan spectrum (SDSS) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Image File history File links Download high-resolution version (850x680, 15 KB)Sloan spectrum (SDSS) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Blazars have highly polarized, variable optical continua. In BL Lac objects, there are no strong emission or absorption lines, while OVV quasars show broad lines.
X-ray Spectra The X-ray spectra of AGNs primarily consist of three components: a power-law component which dominates the X-ray emission in the 0.1-10 keV range, a soft component that sometimes dominates below 1 keV, and an Fe K line feature (6.4 keV). The power-law component is generally seen in all X-ray spectra of optically luminous active galaxies, though it may be hidden by absorption, while the iron feature (an indication of reflection) and soft component are only sometimes seen. AGN with jets have an additional component of nuclear X-ray emission originating in the jet: this may dominate in blazars and core-dominated quasars.
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