Triangulum Galaxy
spiral galaxy in the constellation of Triangulum
The Triangulum Galaxy is a spiral galaxy 2.878 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.
The galaxy is the second-smallest spiral galaxy in the Local Group after the Large Magellanic Cloud, which is a Magellanic-type spiral galaxy. It is believed to be a satellite of the Andromeda Galaxy or on its rebound into the latter due to their interactions, velocities, and proximity to one another in the night sky. It also has an H II nucleus.
Etymology
The galaxy gets its name from the constellation Triangulum, where it can be spotted.
It is sometimes informally referred to as the "Pinwheel Galaxy" by some astronomy references, in some computerized telescope software, and in some public outreach websites. However, the SIMBAD Astronomical Database, a professional database, gathers formal designations for astronomical objects and indicates that Pinwheel Galaxy refers to Messier 101, which several amateur astronomy resources including public outreach websites identify by that name, and that is within the bounds of Ursa Major.
Visibility
Under good viewing conditions with no light pollution, the Triangulum Galaxy can be seen by some people with the fully dark-adapted naked eye; to those viewers, it is the farthest permanent entity visible without magnification, being about half again as distant as Messier 31, the Andromeda Galaxy.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Sep 18, 2026. The linked authority identifier is Q13724. VIAF identifies the subject as 243527874. The Library of Congress control number is sh2001005850. 2 of 2 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Triangulum Galaxy” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.