View source for NGC 681

{{Short description|Spiral galaxy in the constellation Cetus}}
{{Sky|01|49|10.829|-|10|25|35.13}}
__NOTOC__
{{Infobox galaxy
| name=NGC 681
| image=File:NGC 681 legacy dr10.jpg
| appmag_v=12<ref name="professor"/>
| size_v=2.70 × 1.8 [[arcmin]]<ref name="professor"/><ref name="revised"/>
| constellation name=[[Cetus]]
| dec={{DEC|-10|25|35.13}}<ref name="ned"/>
| ra={{RA|01|49|10.829}}<ref name="ned"/>
| dist_ly=~66.5 million [[light-year|ly]] (20.39 ± 1.45 [[parsec|Mpc]])<ref name="ned"/>
| group_cluster = MCG -02-05-053 Group (LGG 33)
| epoch=[[J2000]]
| caption=[[Dark_Energy_Spectroscopic_Instrument#DESI_Legacy_Imaging_Surveys|legacy surveys]] image of NGC 681
| h_radial_v=1760.4 ± 6.6 km/s<ref name="ned"/>
| z=0.00587 ± 0.00002<ref name="ned"/>
| type=[[Intermediate spiral galaxy|SAB(s)ab]]
| size=~29.07 [[parsec|kpc]] (diameter)<ref name="ned"/>
| mass={{val|1.9|e=10}}<ref name="smallsombrero"/>
| mass_light_ratio=3.6<ref name="smallsombrero"/>
| names = {{odlist | IRAS= 01467-1040 | MCG= -02-05-052 | PGC =6671}}<ref>{{cite simbad|title=NGC 681|accessdate=2021-02-19}}</ref>
}}

'''NGC 681''' is an [[intermediate spiral galaxy]] in the [[constellation]] of [[Cetus]], located approximately 66.5 million [[light-year]]s from Earth.<ref name="ned">{{Cite web | url=https://ned.ipac.caltech.edu/?q=byname&obj_sort=RA%20or%20Longitude&out_csys=Equatorial&out_equinox=J2000.0&objname=NGC%20681&hconst=73&extend=no&list_limit=5&img_stamp=YES&of=pre_text&omegav=0.73&corr_z=1&omegam=0.27 | title=NGC 681 NASA/IPAC Extragalactic Database Results |website=ned.ipac.caltech.edu | access-date=November 2, 2018}}</ref><ref name="professor">{{Cite web | url=http://cseligman.com/text/atlas/ngc6a.htm#681 | title=New General Catalog Objects: NGC 650 - 699 | website=cseligman.com|access-date=November 2, 2018}}</ref><ref name="revised">{{Cite web | url=http://spider.seds.org/ngc/revngcic.cgi?NGC681 | title=Revised NGC Data for NGC 681 | website=spider.seds.org | access-date=November 2, 2018}}</ref> 

NGC 681 is a member of the MCG -02-05-053 group (also known as [[Lyons_Groups_of_Galaxies|LGG]] 33), which contains four galaxies, including [[NGC 701]] and [[IC 1738]].<ref>{{cite journal | bibcode=1993A&AS..100...47G | title=General study of group membership. II. Determination of nearby groups | last1=Garcia | first1=A. M. | journal=Astronomy and Astrophysics Supplement Series | date=1993 | volume=100 | page=47}}</ref>

== Observation history ==
NGC 681 was discovered by the German-born British astronomer [[William Herschel]] on 28 November 1785 and was later also observed by William's son, [[John Herschel]].<ref name="professor" /> [[John Louis Emil Dreyer]], compiler of the first ''[[New General Catalogue]] of Nebulae and Clusters of Stars'', described NGC 681 as being a "pretty faint, considerably large, round, small (faint) [[star]] 90 [[Minute and second of arc|arcsec]] to [the] west" that becomes "gradually a little brighter [in the] middle".<ref name="professor" />

== Physical characteristics ==
NGC 681 shares many structural similarities with the Sombrero Galaxy, M104, although it is smaller, less luminous, and less massive. Its thin, dusty [[Galactic disc|disc]] is seen almost perfectly edge-on and features a small, very bright nucleus in the center of a very pronounced [[Bulge (astronomy)|bulge]].<ref name="bigsombrero">{{Cite journal|last=Faber|first=S. M. |last2=Balick |first2=B. |last3=Gallagher|first3=J. S.|last4=Knapp|first4=G. R.|date=1977|title=The neutral hydrogen content, stellar rotation curve, and mass-to-light ratio of NGC 4594, the "Sombrero" galaxy.|journal=The Astrophysical Journal|volume=214|pages=383–389|doi=10.1086/155260|issn=0004-637X|bibcode=1977ApJ...214..383F }}</ref> Distinctly unlike M104, NGC 681's disc contains many [[H II region]]s, where [[star formation]] is likely to be occurring.<ref name="smallsombrero">{{Cite journal|last=Burbridge|first=E. M.|last2=G.R.|first2=Burbridge|last3=Prendergast|first3=K.H.|date=1965|title=Rotation and Mass of the SA Galaxy, NGC 681|url=http://adsbit.harvard.edu//full/1965ApJ...142..154B/0000154.000.html|journal=Astrophysical Journal|volume=142|pages=154–159|bibcode=1965ApJ...142..154B|doi=10.1086/148270|hdl=2060/19650010085|hdl-access=free}}</ref><ref name="bigsombrero" /> The galaxy has a mass of {{Val|1.9e10}} [[Solar mass|<var>M</var><sub>☉</sub>]], a [[mass-to-light ratio]] of 3.6 <math>\Upsilon\odot</math>, and a spiral pattern which is asymmetrical.<ref name="smallsombrero" />{{notelist}}

The [[SIMBAD]] database lists NGC{{nbsp}}681 as a [[Seyfert_galaxy|Seyfert]] II Galaxy, i.e. it has a [[quasar]]-like nucleus with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, the host galaxy is clearly detectable.<ref name="SIMBAD-NGC681"> {{cite simbad | title=NGC 691 | access-date=23 November 2024}}</ref>

==Supernova==
One [[supernova]] has been observed in NGC 681. SN{{nbsp}}2024abup ([[Type_Ib_and_Ic_supernovae|type{{nbsp}}Ib/c]], mag. 17.018) was discovered by [[Asteroid_Terrestrial-impact_Last_Alert_System|ATLAS]] on 22 November 2024.<ref>{{cite web | website=Transient Name Server | title=SN{{nbsp}}2024abup| url=https://www.wis-tns.org/object/2024abup | publisher = [[International_Astronomical_Union|IAU]] | access-date=26 November 2024}}</ref>

==Image gallery==
<gallery>
File:NGC681 - SDSS DR14.jpg|[[Sloan Digital Sky Survey|SDSS]] image of NGC 681
</gallery>

== See also ==
* [[List of NGC objects (1–1000)]]
* [[Sombrero Galaxy]]
* [[Messier object]]
* [[List of spiral galaxies]]

== References ==
{{reflist}}

== External links ==
* {{commonscat-inline}}

{{Catalogs|NGC=681}}
{{NGC10}}
{{Cetus}}

{{DEFAULTSORT:NGC 681}}
[[Category:Galaxies discovered in 1785]]
[[Category:Intermediate spiral galaxies]]
[[Category:Cetus]]
[[Category:Discoveries by William Herschel]]
[[Category:NGC objects|0681]]
[[Category:Principal Galaxies Catalogue objects|006671]]
[[Category:IRAS catalogue objects|01467-1040]]
[[Category:Seyfert galaxies]]