Editing Triangulum Galaxy (section)

{{Short description|Spiral galaxy in the constellation Triangulum}}
{{Sky|01|33|50.9||30|39|36|2810}}
{{Infobox galaxy
| name = Triangulum Galaxy
| image = [[File:VST snaps a very detailed view of the Triangulum Galaxy.jpg|250px]]
| caption = Galaxy Messier 33 in Triangulum (the Triangulum Galaxy)
| epoch = [[Epoch (astronomy)#Julian years and J2000|J2000]]
| pronounce = {{IPAc-en|t|r|aɪ|ˈ|æ|ŋ|ɡ|j|ʊ|l|ə|m}}
| constellation name = [[Triangulum]]
| ra = {{RA|01|33|50.02}}<ref name="SIMBAD-M33"/>
| dec = {{DEC|+30|39|36.7}}<ref name="SIMBAD-M33"/>
| z = {{nowrap|-0.000607 ± 0.000010}}<ref name="SIMBAD-M33"/>
| h_radial_v = {{nowrap|-179 ± 3 [[Metre per second|km/s]]}}<ref name=ned/>
| gal_v = {{nowrap|-44 ± 6 km/s}}<ref name=ned/>
| dist_ly = {{convert|970|kpc|Mly|abbr=on|lk=on }}<ref name=vivian/>
| type = SA(s)cd<ref name=ned/>
| mass = {{Val|5e10}}<ref name=mnras342_1/>
| stars = 40 billion ({{Val|4|e=10}})<ref name=michon/>
| appmag_v = 5.72<ref name="SIMBAD-M33"/>
| size_v = {{nowrap|70.8 × 41.7 [[arcminutes]]}}<ref name="SIMBAD-M33" />
| size = {{cvt|18.74|kpc|ly|sigfig=4|lk=on}}<br />(diameter; 25.0 mag/arcsec<sup>2</sup> B-band isophote)<ref name="RC3">{{Cite book |last1=De Vaucouleurs |first1=Gerard |title=Third Reference Catalogue of Bright Galaxies |last2=De Vaucouleurs |first2=Antoinette |last3=Corwin |first3=Herold G. |last4=Buta |first4=Ronald J. |last5=Paturel |first5=Georges |last6=Fouque |first6=Pascal |year=1991 |bibcode=1991rc3..book.....D}}</ref><ref name=michon/>
| notes =
| names = {{odlist | NGC= 598 | MCG= +05-04-069 | UGC= 1117 | PGC= 5818 | CGCG= 502-110 | IRAS= 01310+3024}}<ref name=ned/>
}}

The '''Triangulum Galaxy''' is a [[spiral galaxy]] 2.73&nbsp;million [[light-year]]s (ly) from Earth in the [[constellation]] [[Triangulum]]. It is catalogued as '''Messier 33''' or '''NGC 598'''. With the D<sub>25</sub> isophotal diameter of {{convert|18.74|kpc|ly|sigfig=3|abbr=off|lk=on}}, 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 spiral|Magellanic-type]] spiral galaxy.<ref name="rydenpeterson">{{Cite book |last1=Ryden |first1=Barbara |author-link1=Barbara Ryden |title=Foundations of astrophysics |last2=Peterson |first2=Bradley M. |date=2010 |publisher=[[Addison-Wesley]] |isbn=978-0-321-59558-4 |location=San Francisco}}</ref> It is believed to be a satellite of the Andromeda Galaxy or on its rebound into the latter due to their interactions, velocities,<ref name="science307_5714" /> and proximity to one another in the night sky. It also has an [[H II region|H II]] [[active galactic nucleus|nucleus]].<ref name="hoetal1997">{{Cite journal |last1=Ho |first1=Luis C. |last2=Filippenko |first2=Alexei V. |last3=Sargent |first3=Wallace L. W. |date=October 1997 |title=A Search for ''Dwarf'' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies |journal=[[The Astrophysical Journal Supplement Series]] |language=en |volume=112 |issue=2 |pages=315–390 |arxiv=astro-ph/9704107 |bibcode=1997ApJS..112..315H |doi=10.1086/313041 |issn=0067-0049 |s2cid=17086638}}</ref>