Barred spiral galaxy

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NGC 1300, viewed nearly face-on; Hubble Space Telescope image

A barred spiral galaxy is a

Milky Way Galaxy, where the Solar System is located, is classified as a barred spiral galaxy.[5]

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.

Although theoretical models of galaxy formation and evolution had not previously expected galaxies becoming stable enough to host bars very early in the universe's history, evidence has recently emerged of the existence of numerous spiral galaxies in the early universe.[6][7][8]

Bars

Further information: Density wave theory § Galactic spiral arms
Barred spiral galaxy IC 5201, located more than 40 million light-years from Earth. It was discovered by Joseph Lunt.[9]

Barred galaxies are apparently predominant, with surveys showing that up to two-thirds of all spiral galaxies develop a bar.[2] 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 farther out, which creates a self-perpetuating bar structure.[10]

The bar structure is believed to act as a type of

Southern Pinwheel Galaxy
.

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. Simulations show that many bars likely experience a "buckling" event in which a disturbance in the orbital resonances of stars in the bar structure leads to an inward collapse in which the bar becomes thicker and shorter though the exact mechanism behind this buckling instability remains hotly debated.[12] Barred spiral galaxies with high mass accumulated in their center thus tend to have short, stubby bars.[13] Such buckling phenomena are significantly suppressed and delayed by the presence of a supermassive black hole in the galactic center but occur nonetheless.[14]

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 average about two billion years.[15]

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.[16]

Milky Way Galaxy spiral arms - based on WISE data.

Grades

NGC 7640 is a barred spiral galaxy in the Andromeda constellation.[17]

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

Example Type Image Information
NGC 2787 SB0 SB0 is a type of lenticular galaxy
NGC 4314 SBa
NGC 4921 SBab
Messier 95 SBb
NGC 3953 SBbc
NGC 1073 SBc
Messier 108 SBcd
NGC 2903 SBd
NGC 5398 SBdm SBdm can also be considered a type

of

barred Magellanic spiral

NGC 55 SBm SBm is a type of Magellanic spiral (Sm)

Other examples

Name Image Type Constellation
M58
 SBc Virgo
M91
 SBb Coma Berenices
M95
 SBb Leo
M109
 SBb Ursa Major
NGC 1300
 SBbc Eridanus
NGC 7541 SB(rs)bcpec Pisces
NGC 1365
 SBc Fornax
NGC 2217
 SBa Canis Major
Magellanic Clouds SBm Dorado, Tucana
UGC 12158 SB Pegasus
NGC 1512[18] SB(r)ab Horologium

See also

References

  1. ^ "Barred spiral galaxy". ScienceDaily. Retrieved 2018-09-17.
  2. ^
    S2CID 189840251
    .
  3. ISBN 978-0-7167-0326-6
    .
  4. ISBN 978-0-6848-3861-8
    .
  5. S2CID 42162871
    .
  6. ^ Milky Way-like galaxy found in the early universe
  7. ^ A Milky Way-like barred spiral galaxy at a redshift of 3
  8. ISSN 2041-8205
    .
  9. ^ "A closer look at IC 5201". www.spacetelescope.org. Archived from the original on 15 December 2016. Retrieved 12 December 2016.
  10. S2CID 17562844
    .
  11. S2CID 10845683
    .
  12. S2CID 182953157
    .
  13. Sky and Telescope
    , April 2002
  14. ISSN 0004-637X
    .
  15. ^ Ripples in a Galactic Pond Archived 2007-09-28 at the Wayback Machine, Scientific American, October 2005
  16. S2CID 14841360
    .
  17. ^ "A spiral in Andromeda". www.spacetelescope.org. Archived from the original on 7 February 2017. Retrieved 6 February 2017.
  18. ^ "Galactic David and Goliath". www.spacetelescope.org. Archived from the original on 2017-09-22. Retrieved 2017-09-22.

External links

Wikimedia Commons has media related to Barred spiral galaxies.
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