Centaurus A
Centaurus A or NGC 5128 is a prominent galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. It is one of the closest radio galaxies to Earth, which means that its galactic nucleus has been extensively studied by professional astronomers. This particular galaxy is also the fifth brightest in the sky. The galaxy contains a supermassive black hole with a mass that is equivalent to 55 million solar masses, which ejects a relativistic jet that is responsible for emissions in the X-ray and radio wavelengths. Like other starburst galaxies, a collision is suspected to be responsible for the intense burst of star formation. Models have suggested that Centaurus A was a large elliptical galaxy which collided and merged with a smaller spiral galaxy. Centaurus A may be described as having a peculiar morphology. As seen from Earth, the galaxy looks like a lenticular or elliptical galaxy with a superimposed dust lane. The peculiarity of this galaxy was first identified in 1847 by John Herschel, and the galaxy was included in Halton Arp's Atlas of
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Peculiar Galaxies (published in 1966) as one of the best examples of a "disturbed" galaxy with dust absorption. The galaxy's strange morphology is generally recognized as the result of a merger between two smaller galaxies.
Schematic diagram of the components of the Centaurus A galaxy
The bulge of this galaxy is composed mainly of evolved red stars.
The dusty disk, however, has been the site of more recent star formation; over 100 star formation regions have been identified in the disk. Two supernovae have been detected in Centaurus A. The first supernova, named SN 1986G, was discovered within the dark dust lane of the galaxy by R. Evans in 1986. It was later identified as a type Ia supernova, which forms when a white dwarf's mass grows large enough to ignite carbon fusion in its center, touching off a runaway thermonuclear reaction, as may happen when a white dwarf in a binary star system strips gas away from the other star. SN 1986G was used to demonstrate that the spectra of type supernovae are not all identical, and that type supernovae may differ in the way that they change in brightness over
time.
The second supernova was discovered by Backyard Observatory Supernova Search in February 2016. Distance estimates to NGC 5128 established since the 1980s typically range between 3–5 Mpc. Classical Cepheids discovered in the heavily-obscured dust lane of NGC 5128 yield a distance between ~3–3.5 Mpc, depending on the nature of the extinction law adopted and other considerations. Mira variables and Type II Cepheids were also discovered in NGC 5128, the latter being rarely detected beyond the Local Group. The distance to NGC 5128 established from several indicators such as Mira variables and planetary nebulae favour a more distant value of ~3.8 Mpc. Centaurus A is at the center of one of two subgroups within the Centaurus A/M83 Group, a nearby group of galaxies. Messier 83 (the Southern Pinwheel Galaxy) is at the center of the other subgroup. These two groups are sometimes identified as one group and sometimes identified as two groups. However, the galaxies around Centaurus A and the galaxies around M83 are physically close to each other, and both subgroups appear not to be moving relative to each other. The Centaurus A/M83 Group is located in the Virgo Supercluster.
Peculiar Galaxies (published in 1966) as one of the best examples of a "disturbed" galaxy with dust absorption. The galaxy's strange morphology is generally recognized as the result of a merger between two smaller galaxies.
Schematic diagram of the components of the Centaurus A galaxy
The bulge of this galaxy is composed mainly of evolved red stars.
The dusty disk, however, has been the site of more recent star formation; over 100 star formation regions have been identified in the disk. Two supernovae have been detected in Centaurus A. The first supernova, named SN 1986G, was discovered within the dark dust lane of the galaxy by R. Evans in 1986. It was later identified as a type Ia supernova, which forms when a white dwarf's mass grows large enough to ignite carbon fusion in its center, touching off a runaway thermonuclear reaction, as may happen when a white dwarf in a binary star system strips gas away from the other star. SN 1986G was used to demonstrate that the spectra of type supernovae are not all identical, and that type supernovae may differ in the way that they change in brightness over
time.
The second supernova was discovered by Backyard Observatory Supernova Search in February 2016. Distance estimates to NGC 5128 established since the 1980s typically range between 3–5 Mpc. Classical Cepheids discovered in the heavily-obscured dust lane of NGC 5128 yield a distance between ~3–3.5 Mpc, depending on the nature of the extinction law adopted and other considerations. Mira variables and Type II Cepheids were also discovered in NGC 5128, the latter being rarely detected beyond the Local Group. The distance to NGC 5128 established from several indicators such as Mira variables and planetary nebulae favour a more distant value of ~3.8 Mpc. Centaurus A is at the center of one of two subgroups within the Centaurus A/M83 Group, a nearby group of galaxies. Messier 83 (the Southern Pinwheel Galaxy) is at the center of the other subgroup. These two groups are sometimes identified as one group and sometimes identified as two groups. However, the galaxies around Centaurus A and the galaxies around M83 are physically close to each other, and both subgroups appear not to be moving relative to each other. The Centaurus A/M83 Group is located in the Virgo Supercluster.