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A barred spiral galaxy is a
Barred galaxies are apparently predominant, with surveys showing that up to two-thirds of all spiral galaxies contain a bar. 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.
The bar structure is believed to act as a type of stellar nursery, channeling gas inwards from the spiral arms through orbital resonance, fueling star birth in the vicinity of its center. This process is also thought to explain why many barred spiral galaxies have active galactic nuclei, such as that seen in the Ripples in a Galactic Pond
, Scientific American, October 2005 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.
"Milky Way’s Central Structure Seen with Fresh Clarity."SPACE.com
16 August 2005. **An article about the Spitzer Space Telescope's Milky Way discovery *Devitt, Terry
16 August 2005. **The original press release regarding the article above, from the Univ. of Wisconsin *'Barred' Spiral Galaxy Pic Highlights Stellar Birth.
SPACE.com
2 March 2001. *Hastings, George and Jane Hastings
1995. "Astronomers Find Multiple Generations of Star Formation in Central Starburst Ring of a Barred Spiral Galaxy." January 15, 2000. **A press release concerning NGC 1326
Barred spirals come and go
'' Sky & Telescope'' April 2002.
"ESO Provides An Infrared Portrait of the Barred Spiral Galaxy Messier 83."
November 29, 2001. **A press release from the
"Spitzer NGC 1291 barred spiral galaxy seen in infrared."
22 October 2014. {{DEFAULTSORT:Barred Spiral Galaxy * * Galaxy morphological types
spiral galaxy
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s. Bars are found in about two thirds of all spiral galaxies, and 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 the Solar System is located, is classified as a barred spiral galaxy.
Edwin Hubble
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an Americans, American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.
Hubble proved that many objects ...
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.
Bars
Barred galaxies are apparently predominant, with surveys showing that up to two-thirds of all spiral galaxies contain a bar. 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.
The bar structure is believed to act as a type of stellar nursery, channeling gas inwards from the spiral arms through orbital resonance, fueling star birth in the vicinity of its center. 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
Messier 83 or M83, also known as the Southern Pinwheel Galaxy and NGC 5236, is a barred spiral galaxy approximately 15 million light-years away in the constellation borders of Hydra and Centaurus. Nicolas-Louis de Lacaille discovered M83 on ...
.
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., Scientific American, October 2005 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.
Grades
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.
Examples
Other examples
See also
* Galaxy morphological classification * Galaxy formation and evolution *IC 1011
IC 1011 is a barred spiral galaxy with apparent magnitude of 14.7, and with a redshift of z=0.02564 (SIMBAD) or 0.025703 (NASA),
* Lenticular galaxy
* Firehose instability
References
External links
*Britt, Robert Roy"Milky Way’s Central Structure Seen with Fresh Clarity."
16 August 2005. **An article about the Spitzer Space Telescope's Milky Way discovery *Devitt, Terry
16 August 2005. **The original press release regarding the article above, from the Univ. of Wisconsin *'Barred' Spiral Galaxy Pic Highlights Stellar Birth.
SPACE.com
2 March 2001. *Hastings, George and Jane Hastings
1995. "Astronomers Find Multiple Generations of Star Formation in Central Starburst Ring of a Barred Spiral Galaxy." January 15, 2000. **A press release concerning NGC 1326
Barred spirals come and go
'' Sky & Telescope'' April 2002.
"ESO Provides An Infrared Portrait of the Barred Spiral Galaxy Messier 83."
November 29, 2001. **A press release from the
European Southern Observatory
The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...
.
*Horton, Adam"Spitzer NGC 1291 barred spiral galaxy seen in infrared."
22 October 2014. {{DEFAULTSORT:Barred Spiral Galaxy * * Galaxy morphological types