Intermediate spiral galaxy

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Messier 83 is an intermediate spiral galaxy of type SABc located in the constellation Hydra. M83 - Southern Pinwheel.jpg
Messier 83 is an intermediate spiral galaxy of type SABc located in the constellation Hydra.

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. [1] 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.

Diagram of the Hubble - de Vaucouleurs morphological classification system illustrating the class of intermediate spirals. Hubble - de Vaucouleurs Galaxy Morphology Diagram.png
Diagram of the Hubble - de Vaucouleurs morphological classification system illustrating the class of intermediate spirals.


Example Type ImageInformationNotes
SAB0-SAB0- is a type of lenticular galaxy
SAB0SAB0 is a type of lenticular galaxy
SAB0+SAB0+ is a type of lenticular galaxy
SAB0/aSAB0/a can also be considered a type of intermediate lenticular galaxy
Messier 65 SABa Messier object 065.jpg M65 is an "SAB(rs)a"
NGC 4725 SABab NGC 4725.jpg NGC 4725 is an "SAB(r)ab pec"
Messier 66 SABb Phot-33c-03-fullres.jpg M66 is an "SAB(s)b"
Messier 106 SABbc NGC 4258GALEX.jpg M106 is an "SAB(s)bc"
Sculptor Galaxy SABc Ngc253 2mass barred spiral.jpg Sculptor is an "SAB(s)c"
NGC 2403 SABcd NGC2403 3.6 8.0 24 microns spitzer.png NGC 2403 is an "SAB(s)cd"
SABdmSABdm can also be considered a type of intermediate Magellanic spiral
NGC 4625 SABm NGC 4625 I FUV g2006.jpg SABm is a type of Magellanic spiral (Sm)NGC 4625 is an "SAB(rs)m pec"
Fireworks Galaxy SAB(rs)cd NGC6946 Galaxy from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block.jpg NGC 4625 is an "SAB(rs)cd"

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Hubble sequence

The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. It is often colloquially known as the Hubble tuning fork diagram because the shape in which it is traditionally represented resembles a tuning fork. In June 2019, however, citizen scientists through Galaxy Zoo reported that the usual Hubble classification, particularly concerning spiral galaxies, may not be supported, and may need updating.

Spiral galaxy

Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often surrounded by a much fainter halo of stars, many of which reside in globular clusters.

Irregular galaxy

An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.

Messier 83

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 February 23, 1752 at the Cape of Good Hope. Charles Messier added it to his catalogue of nebulous objects in March 1781. It is one of the closest and brightest barred spiral galaxies in the sky, and is visible with binoculars. Its nickname of the Southern Pinwheel derives from its resemblance to the Pinwheel Galaxy (M101).

Messier 61

Messier 61 is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was discovered by Barnaba Oriani on May 5, 1779. This was six days before Charles Messier observed the same galaxy, but had mistaken it as a comet.

Black Eye Galaxy

The Black Eye Galaxy is a relatively isolated spiral galaxy located 17 million light-years away in the northern constellation of Coma Berenices. It was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier in 1780. A dark band of absorbing dust in front of the galaxy's bright nucleus gave rise to its nicknames of the "Black Eye" or "Evil Eye" galaxy. M64 is well known among amateur astronomers because of its appearance in small telescopes.

Galaxy morphological classification System for categorizing galaxies based on appearance

Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by Gérard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology.

Messier 77

Messier 77 or M77, also known as NGC 1068, is a barred spiral galaxy about 47 million light-years away in the constellation Cetus. Messier 77 was discovered by Pierre Méchain in 1780, who originally described it as a nebula. Méchain then communicated his discovery to Charles Messier, who subsequently listed the object in his catalog. Both Messier and William Herschel described this galaxy as a star cluster. Today, however, the object is known to be a galaxy.

NGC 1 Spiral galaxy in the constellation Pegasus

NGC 1, also occasionally referred to as GC 1, UGC 57, PGC 564 or Holm 2a is an intermediate spiral galaxy of the morphological type Sbc, located approximately 210 to 215 million light-years from the Solar System in the constellation Pegasus. It was discovered on 30 September 1861 by Heinrich d'Arrest.

Disc galaxy A galaxy characterized by a flattened circular volume of stars, that may include a central bulge

A disc galaxy is a galaxy characterized by a galactic disc, a flattened circular volume of stars. These galaxies may or may not include a central non-disc-like region.

NGC 1637

NGC 1637 is an isolated, non-interacting intermediate spiral galaxy in the constellation Eridanus, about a degree to the WNW of the star Mu Eridani. It is located at a distance of about 9.77 ± 1.82 Mpc (31.9 ± 5.9 Mly) from the Milky Way. The galaxy is inclined at an angle of 31.1° to the line of sight from the Earth and the long axis is oriented along a position angle of 16.3°.

NGC 2903

NGC 2903 is an isolated barred spiral galaxy in the equatorial constellation of Leo, positioned about 1.5° due south of Lambda Leonis. It was discovered by German-born astronomer William Herschel, who cataloged it on November 16, 1784. He mistook it as a double nebula, as did subsequent observers, and it wasn't until the nineteenth century that the Third Earl of Rosse resolved into a spiral form. J. L. E. Dreyer assigned it the identifiers 2903 and 2905 in his New General Catalogue; NGC 2905 now designates a luminous knot in the northeastern spiral arm.

NGC 2997

NGC 2997 is a face-on unbarred spiral galaxy about 40 million light-years away in the faint southern constellation of Antlia. It was discovered March 4, 1793 by German-born astronomer William Herschel. J. L. E. Dreyer described it as, "a remarkable object, very faint, very large, very gradually then very suddenly bright middle and 4 arcsec nucleus. This is the brightest galaxy of the NGC 2997 group of galaxies, and was featured on the cover of the first edition of Galactic Dynamics by James Binney and Scott Tremaine.

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.

NGC 10 Spiral galaxy in the constellation Sculptor

NGC 10 is a spiral galaxy located in the southern constellation of Sculptor. It was discovered by John Herschel on 25 September 1834. The galaxy is located at a distance of 346 Mly from the Sun. Its morphological classification in the De Vaucouleurs system is SAB(rs)bc, where the 'SAB' denotes a weak-barred spiral, '(rs)' indicates a slight ring-like structure, and 'bc' means the spiral arms are moderately to loosely wound. Paturel et al. (2003) assigned this galaxy a classification of SBbc, indicating a barred spiral galaxy.

Eridanus Cluster Galaxy cluster

The Eridanus Cluster is a galaxy cluster roughly 23 Mpc (75 Mly) from Earth, containing about 73 main galaxies and about 200 total galaxies. About 30% have Hubble classifications of elliptical or S0 and the remaining 70% are spiral or irregular. These galaxies reside in smaller groups which are all loosely gravitationally bound to each other, suggesting that the system is still condensing from the Hubble flow and may eventually form a cluster of about 1014M. A low velocity dispersion compared to that of, for example, the Coma cluster, supports this hypothesis. The Eridanus Cluster is located in the constellation Eridanus near the Fornax Cluster, and is sometimes called the "Fornax II Cluster".

Magellanic spiral galaxies are (usually) dwarf galaxies which are classified as the type Sm. 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.

NGC 4535 Galaxy in the constellation Virgo

NGC 4535 is a barred spiral galaxy located some 54 million light years from Earth in the constellation Virgo. It is a member of the Virgo Cluster of galaxies and is located 4.3° from Messier 87. The galactic plane of NGC 4535 is inclined by an angle of 43° to the line of sight from the Earth. The morphological classification of NGC 4535 in the De Vaucouleurs system is SAB(s)c, which indicates a bar structure across the core (SAB), no ring (s), and loosely wound spiral arms (c). The inner part of the galaxy has two spiral arms, which branch into multiple arms further away. The small nucleus is of type HII, meaning the spectrum resembles that of an H II region.

NGC 765

NGC 765 is an intermediate spiral galaxy located in the constellation Aries. It is located at a distance of circa 220 million light years from Earth, which, given its apparent dimensions, means that NGC 765 is about 195,000 light years across. It was discovered by Albert Marth on October 8, 1864. The galaxy has an extensive hydrogen (HI) disk with low surface brightness, whose diameter is estimated to be 240 kpc.

NGC 585

NGC 585 is a spiral galaxy in the constellation of Cetus, which is about 245 million light-years from the Milky Way 's center. The object was discovered on December 20, 1827 by the British astronomer John Frederick William Herschel.


  1. de Vaucouleurs, Gerard (1963). "Revised Classification of 1500 Bright Galaxies". Astrophysical Journal Supplement. 8: 31. Bibcode:1963ApJS....8...31D. doi:10.1086/190084.