Editing Equuleus (section)

==Notable features==
[[Image:EquuleusCC.jpg|thumb|left|256px|The constellation Equuleus as it can be seen by the naked eye.]]

[[Image:Equuleus 20191202.jpg|thumb|right|256px|The constellation Equuleus, color and contrast enhanced.]]

===Stars===
{{see|List of stars in Equuleus}}
The brightest star in Equuleus is [[Alpha Equulei|α Equulei]], traditionally called Kitalpha, a yellow star magnitude 3.9, 186 light-years from Earth. Its traditional name means "the section of the horse".{{sfn|Ridpath|Tirion|2001|pp=144-145}}

There are few [[variable star]]s in Equuleus.  Only around 25 are known, most of which are faint. [[Gamma Equulei|γ Equulei]] is an [[Alpha2 Canum Venaticorum variable|α<sup>2</sup> CVn variable star]], ranging between magnitudes 4.58 and 4.77<ref>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref> over a period of around 12½ minutes.<!-- not cited to Ridpath and Tirion 2001 --> It is a white star 115 light-years from Earth, and has an [[optical binary|optical companion]] of magnitude 6.1, [[6 Equulei]]. It is divisible in binoculars.{{sfn|Ridpath|Tirion|2001|pp=144-145}} 6 Equulei is an astrometric binary system itself,<ref name=Frankowski2007>{{citation | last1=Frankowski | first1=A. | last2=Jancart | first2=S. | last3=Jorissen | first3=A. | title=Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data | journal=Astronomy and Astrophysics | volume=464 | issue=1 | pages=377–392 |date=March 2007 | doi=10.1051/0004-6361:20065526 | bibcode=2007A&A...464..377F |arxiv = astro-ph/0612449 | s2cid=14010423 }}</ref> with an apparent magnitude of 6.07.<ref name=clpl4_99>{{citation | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | year=1966 | page=99 | bibcode=1966CoLPL...4...99J }}</ref> [[R Equulei]] is a [[Mira variable]] that ranges between magnitudes 8.0 and 15.7<ref name=REqu /> over nearly 261 days. It has a spectral type of M3e-M4e<ref name=REqu>{{citation|postscript=.|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=B/gcvs|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref> and has an average B-V colour index of +1.41.<ref name=Zacharias_et_al_2012>{{citation
 | title=The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)
 | display-authors=1 | last1=Zacharias | first1=N.
 | last2=Finch | first2=C. T. | last3=Girard | first3=T. M.
 | last4=Henden | first4=A. | last5=Bartlett | first5=J. L.
 | last6=Monet | first6=D. G. | last7=Zacharias | first7=M. I.
 | journal=VizieR On-line Data Catalog
 | volume=1322 | date=2012 | issue=2 | page=44 | doi=10.1088/0004-6256/145/2/44 | postscript=.
 | bibcode=2012yCat.1322....0Z | arxiv=1212.6182 | s2cid=119299381 }}</ref>

Equuleus contains some [[double star]]s of interest.  γ Equulei consists of a primary star with a magnitude around 4.7 (slightly variable) and a secondary star of magnitude 11.6, separated by 2 [[arcsecond]]s.  [[Epsilon Equulei|ε Equulei]] is a triple star also designated 1 Equulei. The system, 197 light-years away, has a primary of magnitude 5.4 that is itself a binary star; its components are of magnitude 6.0 and 6.3 and have a period of 101 years. The secondary is of magnitude 7.4 and is visible in small telescopes. The components of the primary are becoming closer together and will not be divisible in amateur telescopes beginning in 2015.{{sfn|Ridpath|Tirion|2001|pp=144-145}} [[Delta Equulei|δ Equulei]] is a [[binary star]] with an orbital period of 5.7 years, which at one time was the shortest known orbital period for an optical binary. The two components of the system are never more than 0.35 arcseconds apart.

===Deep-sky objects===
Due to its small size and its distance from the plane of the [[Milky Way]], Equuleus is rather devoid of [[deep sky objects]] such as [[star clusters]] and [[nebulae]]. Some very faint [[galaxy|galaxies]] in the [[New General Catalogue]] between [[Apparent magnitude|magnitudes]] 13 and 15 include [[NGC 7015]], [[NGC 7040]], and [[NGC 7046]]. [[NGC 7045]] is a [[triple star]] that was mistaken as a nebula by its discoverer, [[John Herschel]].<ref>{{Cite web |date= |title=NGC 7045 Basic Information |url=http://ngcicproject.observers.org/NGC/NGC_70xx/NGC_7045.htm |access-date=2024-03-25 |website=The NGC/IC Project}}</ref> Other faint galaxies in the [[Index Catalogue]] include IC 1360, IC 1361, IC 1364, IC 1367, IC 1375, and IC 5083. IC 1365 is a group of galaxies. The magnitudes of these objects vary from 14.5 to 15.5, making them hard to see in even the largest of [[Amateur astronomy|amateur]] telescopes.<ref>{{Cite web |title=Deep sky objects in Equuleus - Full list |url=https://theskylive.com/sky/constellations/equuleus-deepsky-objects |access-date=2024-03-25 |website=The Sky Live}}</ref>