A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in between one third and two thirds of all spiral galaxies. Bars generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well. The Milky Way Galaxy, where our own Solar System is located, is classified as a barred spiral galaxy.
Edwin Hubble classified spiral galaxies of this type as "SB" (spiral, barred) in his Hubble sequence and arranged them into sub-categories based on how open the arms of the spiral are. SBa types feature tightly bound arms, while SBc types are at the other extreme and have loosely bound arms. SBb-type galaxies lie in between the two. SB0 is a barred lenticular galaxy. A new type, SBm, was subsequently created to describe somewhat irregular barred spirals, such as the Magellanic Clouds, which were once classified as irregular galaxies, but have since been found to contain barred spiral structures. Among other types in Hubble's classifications for the galaxies are the spiral galaxy, elliptical galaxy and irregular galaxy.
Barred galaxies are apparently predominant, with surveys showing that up to two-thirds of all spiral galaxies contain a bar. The current hypothesis is that the bar structure acts as a type of stellar nursery, fueling star birth at their centers. The bar is thought to act as a mechanism that channels gas inwards from the spiral arms through orbital resonance, in effect funneling the flow to create new stars. This process is also thought to explain why many barred spiral galaxies have active galactic nuclei, such as that seen in the Southern Pinwheel Galaxy.
The creation of the bar is generally thought to be the result of a density wave radiating from the center of the galaxy whose effects reshape the orbits of the inner stars. This effect builds over time to stars orbiting further out, which creates a self-perpetuating bar structure.
Bars are thought to be temporary phenomena in the lives of spiral galaxies; the bar structures decay over time, transforming galaxies from barred spirals to more "regular" spiral patterns. Past a certain size the accumulated mass of the bar compromises the stability of the overall bar structure. Barred spiral galaxies with high mass accumulated in their center tend to have short, stubby bars. Since so many spiral galaxies have bar structures, it is likely that they are recurring phenomena in spiral galaxy development. The oscillating evolutionary cycle from spiral galaxy to barred spiral galaxy is thought to take on the average about two billion years.
Recent studies have confirmed the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end. A 2008 investigation found that only 20 percent of the spiral galaxies in the distant past possessed bars, compared with about 65 percent of their local counterparts.
The general classification is "SB" (spiral barred). The sub-categories are based on how open or tight the arms of the spiral are. SBa types feature tightly bound arms. SBc types are at the other extreme and have loosely bound arms. SBb galaxies lie in between. SBm describes somewhat irregular barred spirals. SB0 is a barred lenticular galaxy.
|NGC 2787||SB0||SB0 is a type of lenticular galaxy|
|NGC 5398||SBdm||SBdm can also be considered a type|
|NGC 55||SBm||SBm is a type of Magellanic spiral (Sm)|
|NGC 2217||SBa||Canis Major|
|Magellanic Clouds||SBm||Dorado, Tucana|
A barred irregular galaxy is an irregular version of a barred spiral galaxy. Examples include the Large Magellanic Cloud and NGC 6822. Some barred irregular galaxies (like the Large Magellanic Cloud) may be dwarf spiral galaxies, which have been distorted into an irregular shape by tidal interactions with a more massive neighbor.Dwarf spiral galaxy
A dwarf spiral galaxy is the dwarf version of a spiral galaxy. Dwarf galaxies are characterized as having low luminosities, small diameters (less than 5 kpc), low surface brightnesses, and low hydrogen masses. The galaxies may be considered a subclass of low-surface-brightness galaxies.
Dwarf spiral galaxies, particularly the dwarf counterparts of Sa-Sc type spiral galaxies, are quite rare. In contrast, dwarf elliptical galaxies, dwarf irregular galaxies, and the dwarf versions of Magellanic type galaxies (which may be considered transitory between spiral and irregular in terms of morphology) are very common.It is suggested that dwarf spiral galaxies can transform into dwarf elliptical galaxies, especially in dense cluster environments.Intermediate spiral galaxy
An intermediate spiral galaxy is a galaxy that is in between the classifications of a barred spiral galaxy and an unbarred spiral galaxy. It is designated as SAB in the galaxy morphological classification system devised by Gerard de Vaucouleurs. Subtypes are labeled as SAB0, SABa, SABb, or SABc, following a sequence analogous to the Hubble sequence for barred and unbarred spirals. The subtype (0, a, b, or c) is based on the relative prominence of the central bulge and how tightly wound the spiral arms are.Magellanic spiral
Magellanic spiral galaxies are (usually) dwarf galaxies which are classified as the type Sm (and SAm, SBm, SABm). They are galaxies with one single spiral arm, and are named after their prototype, the Large Magellanic Cloud, an SBm galaxy. They can be considered to be intermediate between dwarf spiral galaxies and irregular galaxies.Messier 109
Messier 109 (also known as NGC 3992) is a barred spiral galaxy exhibiting a weak inner ring structure around the central bar approximately 83.5 ± 24 million light-years away in the constellation Ursa Major. M109 can be seen southeast of the star Phecda (γ UMa).NGC 1073
NGC 1073 is a barred spiral galaxy in the constellation Cetus. It probably has an H II nucleus.
NGC 1073 is about 55 million light years from Earth. NGC 1073 is about 80,000 light years across. NGC 1073 can be viewed with a mid-sized telescope and is found in the Cetus constellation, also called the Sea Monster. NGC 1073 is a barred spiral galaxy like the Milky Way; unlike the Milky Way, however, NGC 1073 does not have well formed symmetrical arms and the center bar is larger.NGC 1300
NGC 1300 is a barred spiral galaxy located about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across (about the same size of the Milky Way). It is a member of the Eridanus Cluster, a cluster of 200 galaxies. It was discovered by John Herschel in 1835.In the core of the larger spiral structure of NGC 1300, the nucleus shows a "grand-design" spiral structure that is about 3,300 light-years long. Only galaxies with large-scale bars appear to have these grand-design inner disks — a spiral within a spiral. Models suggest that the gas in a bar can be funneled inwards, and then spiral into the center through the grand-design disk, where it can potentially fuel a central supermassive black hole (SMBH). NGC 1300 is not known to have an active nucleus, indicating that its central black hole is not accreting matter. The SMBH has a mass of 7.3+6.9−3.5×107 M☉.NGC 1365
NGC 1365, also known as the Great Barred Spiral Galaxy, is a barred spiral galaxy about 56 million light-years away in the constellation Fornax.
The core is an oval shape with an apparent size of about 50″ × 40″.
The spiral arms extend in a wide curve north and south from the ends of the east-west bar and form an almost ring like Z-shaped halo.Supernovae 2012fr, 2001du, 1983V, and 1957C were observed in NGC 1365.
The central supermassive black hole in the active nucleus, measured to be about 2 million solar masses in size, rotates close to the relativistic limit (the dimensionless spin parameter is larger than 0.84). These observations, announced in February 2013, were made using the X-ray telescope satellite NuSTAR.NGC 139
NGC 139 is a barred spiral galaxy in the constellation Pisces. It was discovered on August 29, 1864 by the German astronomer Albert Marth.NGC 165
NGC 165 is a barred spiral galaxy located in the constellation Cetus. It was discovered in 1882 by Wilhelm Tempel and was described by as "faint, large, star in centre, eastern of 2" by John Louis Emil Dreyer.NGC 3059
NGC 3059 is a barred spiral galaxy. It is located in the constellation of Carina. The galaxy can be described as being faint, large, and irregularly round. It was discovered on February 22, 1835 by John Herschel.NGC 4440
NGC 4440 is a barred spiral galaxy located about 55 million light-years away in the constellation of Virgo. NGC 4440 was discovered by astronomer William Herschel on April 17, 1784. It is a member of the Virgo Cluster.NGC 4454
NGC 4454 is a barred spiral galaxy located about 123 million light-years away in the constellation of Virgo. NGC 4454 was discovered by astronomer William Herschel on April 17, 1784.NGC 4907
NGC 4907 is a barred spiral galaxy located about 270 million light-years away in the constellation of Coma Berenices. It is also classified as a LINER galaxy. NGC 4907 was discovered by astronomer Heinrich d'Arrest on May 5, 1864. The galaxy is a member of the Coma Cluster.NGC 64
NGC 64 is a barred spiral galaxy discovered by Lewis Swift in 1886, and is located in the Cetus constellation.NGC 7051
NGC 7051 is a barred spiral galaxy located about 100 million light-years away in the constellation of Aquarius. It was discovered by astronomer John Herschel on July 30, 1827.NGC 7065
NGC 7065 Is a barred spiral galaxy located about 320 million light-years away in the constellation of Aquarius. NGC 7065 is part of a pair of galaxies that contains the galaxy NGC 7065A. NGC 7065 was discovered by astronomer Albert Marth on August 3, 1864.NGC 7301
NGC 7301 is a barred spiral galaxy located around 308,000,000 light-years (94,000,000 pc) away from Earth in the constellation Aquarius. It was discovered by American astronomer Francis Preserved Leavenworth In 1886.Unbarred spiral galaxy
An unbarred spiral galaxy is a type of spiral galaxy without a central bar, or one that is not a barred spiral galaxy. It is designated with an SA in the galaxy morphological classification scheme.
The Sombrero Galaxy is an unbarred spiral galaxy.
Barless spiral galaxies are one of three general types of spiral galaxies under the de Vaucouleurs system classification system, the other two being intermediate spiral galaxy and barred spiral galaxy. Under the Hubble tuning fork, it is one of two general types of spiral galaxy, the other being barred spirals.