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Glossary term: Disk Galaxy

Description: A disk galaxy is a type of galaxy that features a flat component of stars, gas, and dust, all of which are in circular coplanar motion around the galaxy's center. Spiral arms and associated star-forming activity are often present in these disks. In most galaxy classification schemes, disk galaxies are differentiated from elliptical, irregular, and dwarf galaxies.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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This galaxy has a large bulge surrounded by a ring of dust creating an image similar to the mexican hat with the same name

Sombrero galaxy

Caption: This prominent galaxy M 104 is often called the Sombrero galaxy due to its resemblance to the Mexican hat. This look is created by the thin disk oriented nearly edge-on, which appears illuminated by the dominant bulge. Both, the disk and bulge contain stars, but the stars in the bulge tend to be older, while the disk also harbors large amounts of dust and gas creating shadows. M 104 is located in the constellation Virgo approximately 50 light-years away. While some of the dots visible in the picture are foreground stars and others background galaxies, the majority are actually globular clusters, dense massive clusters of stars, associated with the Sombrero Galaxy.
Credit: ESO/P. Barthel credit link

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Andromeda is a bright disk, with dark spiral lines in it, tilted up at the west end. Two small bright blobs lie left & right

A visible light image of the Andromeda Galaxy

Caption: The Andromeda Galaxy viewed in visible light. Like our Milky Way, Andromeda is a barred spiral galaxy. Here we can see its bright core and spiral disk. The glow from the stars in the disk is interrupted by lanes of dust that form part of its spiral structure. Andromeda is the largest galaxy in the Local Group of galaxies that includes the Milky Way. To the left of the core and just above the disk we see the dwarf galaxy M32 and to the right and below the disk we see the dwarf galaxy M110. These are both satellite galaxies of the Andromeda Galaxy.
Credit: Torben Hansen credit link

License: CC-BY-2.0 Creative Commons Attribution 2.0 Generic icons


The bright core of this galaxy is surrounded by a much fainter disk. This faint disk has thin dark rings.

The Lenticular Galaxy NGC 2787

Caption: The lenticular galaxy NGC 2787. This galaxy is a disk galaxy but lacks the large, dominant spiral arm structure seen in the disks of spiral galaxies. Its core is very bright compared to the core of a spiral galaxy. Thin rings of dust can be seen in the galaxy's disk.
Credit: NASA/ESA and The Hubble Heritage Team credit link

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

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