Editing Triangulum (section)

===Deep-sky objects===
[[File:The peculiar asymmetry of NGC 949.jpg|thumb|The peculiar asymmetry of [[NGC 949]].<ref>{{cite web|title=The peculiar asymmetry of NGC 949|url=http://www.spacetelescope.org/images/potw1518a/|access-date=14 June 2015}}</ref>]]

The [[Triangulum Galaxy]], also known as Messier 33, was discovered by [[Giovanni Battista Hodierna]] in the 17th century.<ref name=jha16_1>{{cite journal | first1=G.|first2=L.|first3= P. | title=Hodierna's Observations of Nebulae and his Cosmology | journal=Journal for the History of Astronomy | volume=16 | issue=1 |date=February 1985 | pages=1–36 | bibcode=1985JHA....16....1F | last2=Indorato | last3=Nastasi | last1=Fodera-Serio |doi=10.1177/002182868501600101|s2cid=118328541| doi-access=free }}</ref> A distant member of the [[Local Group]], it is about 2.3 million light-years away, and at magnitude 5.8 it is bright enough to be seen by the naked eye under dark skies. Being a diffuse object, it is challenging to see under [[Light pollution|light-polluted]] skies, even with a small telescope or binoculars, and low power is required to view it. It is a [[spiral galaxy]] with a diameter of 46,000 light-years and is thus smaller than both the [[Andromeda Galaxy]] and the [[Milky Way]]. A distance of less than 300 [[parsec|kiloparsecs]] between it and Andromeda supports the hypothesis that it is a satellite of the larger galaxy.<ref name="pawlowski">{{cite journal|author=Pawlowski, Marcel S.|author2=Kroupa, Pavel|author3=Jerjen, Helmut |date=2013|title=Dwarf Galaxy Planes: the Discovery of Symmetric Structures in the Local Group|journal=Monthly Notices of the Royal Astronomical Society|volume=435|issue=3|pages=1928|arxiv=1307.6210|doi=10.1093/mnras/stt1384|doi-access=free |bibcode = 2013MNRAS.435.1928P |s2cid=53991672}}</ref> It is believed to have been interacting with it from their velocities.<ref name=science307_5714>{{cite journal | author=Brunthaler, Andreas | display-authors=4 | author2=Reid, Mark J. | author3=Falcke, Heino | author4=Greenhill, Lincoln J.| author5=Henkel, Christian | date=2005 | title=The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33) | journal=Science | volume=307 | issue=5714 | pages=1440–1443 | bibcode=2005Sci...307.1440B | doi=10.1126/science.1108342 | pmid=15746420|arxiv = astro-ph/0503058 | s2cid=28172780 }}</ref> Within the constellation, it lies near the border of Pisces, 3.5 degrees west-northwest of Alpha Trianguli and 7 degrees southwest of [[Beta Andromedae]].<ref name="motz"/> Within the galaxy, [[NGC 604]] is an [[H II region]] where star formation takes place.<ref>{{Cite APOD|title=NGC 604: Giant Stellar Nursery in M33 |date=16 August 1996 |access-date=8 September 2013}}</ref><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 = Astrophysical Journal Supplement| volume = 112| pages = 315–390| bibcode = 1997ApJS..112..315H| doi = 10.1086/313041| issue = 2 |arxiv = astro-ph/9704107 | s2cid = 17086638}}</ref>

[[File:A distorted duo IC 1727 UGC 1249.jpg|left|thumb|[[IC 1727]] and [[UGC 1249]].<ref>{{cite web|title=A distorted duo|url=https://www.spacetelescope.org/images/potw1733a/|website=www.spacetelescope.org|access-date=14 August 2017}}</ref>]]

In addition to M33, there are several NGC galaxies of visual magnitudes 12 to 14.<ref name=garfinckle1997/> The largest of these include the 10 [[minute of arc|arcminute]] long magnitude 12 [[NGC 925]] spiral galaxy and the 5 arcminute long magnitude 11.6 [[NGC 672]] barred spiral galaxy. The latter is close by and appears to be interacting with [[IC 1727]]. The two are 88,000 light-years apart and lie around 18 million light-years away.<ref>{{cite web|url=http://www.noao.edu/outreach/aop/observers/n672.html|title=NGC 672|last=Block|first=Adam|date=20 October 2003|publisher=National Optical Astronomy Observatory|access-date=8 September 2013|archive-date=24 May 2015|archive-url=https://web.archive.org/web/20150524081149/http://www.noao.edu/outreach/aop/observers/n672.html|url-status=dead}}</ref> These two plus another four nearby dwarf irregular galaxies constitute the NGC 672 group, and all six appear to have had a burst of star formation in the last ten million years. The group is thought connected to another group of six galaxies known as the NGC 784 group, named for its principal galaxy, the barred spiral [[NGC 784]]. Together with two isolated dwarf galaxies, these fourteen appear to be moving in a common direction and constitute a group possibly located on a [[dark matter]] [[Galaxy filament|filament]].<ref>{{cite journal|author =Zitrin, Adi|author2 =Brosch, Noah |date=2008|title=The NGC 672 and 784 galaxy groups: evidence for galaxy formation and growth along a nearby dark matter filament|journal=Monthly Notices of the Royal Astronomical Society |volume=390|issue=1|pages=408–20|doi=10.1111/j.1365-2966.2008.13786.x|doi-access =free |arxiv = 0808.1789 |bibcode = 2008MNRAS.390..408Z |s2cid =16296617 }}</ref> [[3C 48]] was the first [[quasar]] ever to be observed, although its true identity was not uncovered until after that of [[3C 273]] in 1963.<ref>{{cite book|last=Robertson|first=Peter |title=Beyond Southern Skies: Radio Astronomy and the Parkes Telescope|publisher=Cambridge University Press|location=Cambridge, United Kingdom| date=1992|page=234|isbn=0-521-41408-3|url=https://books.google.com/books?id=OBOY2G_3BCgC&q=3C+48&pg=PA234}}</ref> It has an apparent magnitude of 16.2 and is located about 5 degrees northwest of Alpha Trianguli.<ref name="motz"/>

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