Glossary term: Spiral Galaxy

Redirected from Spiral Arm

Description: Spiral galaxies are galaxies that have spiral arms: regions of higher density that form as a galaxy rotates where gas and dust are compressed and new stars are born. Most spiral galaxies are disk galaxies, so the names are sometimes used interchangeably. Most spiral galaxies have a central bulge of stars, and many (including the Milky Way) have a central bar. Spiral galaxies are differentiated from elliptical, lenticular, irregular, and dwarf galaxies (though dwarf spiral galaxies also exist).

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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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Two spiral galaxies embracing in their early stages of merger with distortions on the smaller galaxy visible

Spiral Galaxy Merger

Caption: This image shows two interacting spiral galaxies located approximately 150 million light-years away. Two spiral galaxies are involved in this dance, creating visible distortions in their spiral arms due to the gravitational pull. What is starting as an embrace in this picture, will end in the merger of those two galaxies into one, most likely elliptical, galaxy.
Credit: ESO credit link

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