View source for Astronomy:NGC 4631

{{Short description|Galaxy in the constellation Canes Venatici}}
{{Infobox Galaxy
| name = [[Astronomy:New General Catalogue|NGC]] 4631
| image = NGC 4631 HST.jpg
| image_size = 300px
|caption = An image of NGC 4631 taken with [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]]
| constellation name = [[Astronomy:Canes Venatici|Canes Venatici]]<ref name="sinnott1988">{{cite book 
  | editor=R. W. Sinnott
  | title= The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer
  | date=1988
  | publisher=Sky Publishing Corporation and Cambridge University Press
  | isbn=978-0-933346-51-2}}</ref>
| epoch = [[Astronomy:J2000|J2000]]
| type = SB(s)d<ref name="ned">{{cite web
  | title=NASA/IPAC Extragalactic Database
  | work=Results for NGC 4631
  | url=http://nedwww.ipac.caltech.edu/
  | access-date=2006-11-21}}</ref>
| ra = {{RA|12|42|08.0}}<ref name="ned" />
| dec = {{DEC|+32|32|29}}<ref name="ned" />
| dist_ly = 30 [[Astronomy:Light-year|Mly]]
| z = 606 ± 3 km/[[Second|s]]<ref name="ned" />
| appmag_v = 9.8<ref name="ned" />
| size_v = 15′.5 × 2′.7<ref name="ned" />
| notes = edge-on
| names = Whale Galaxy,<ref name="simbad" /> [[Astronomy:Uppsala General Catalogue|UGC]] 7865,<ref name="ned" /> [[Astronomy:Principal Galaxies Catalogue|PGC]] 42637,<ref name="ned" /> [[Astronomy:Atlas of Peculiar Galaxies|Arp]] 281,<ref name="ned" /> [[Astronomy:Caldwell catalogue|Caldwell]]&nbsp;32
}}

'''NGC 4631''' (also known as the '''Whale Galaxy''' or '''Caldwell 32''') is a  [[Astronomy:Barred spiral galaxy|barred spiral galaxy]] in the [[Astronomy:Constellation|constellation]] [[Astronomy:Canes Venatici|Canes Venatici]] about 30 million light years away from Earth. This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, hence its nickname.<ref name="simbad">{{cite simbad
  | title=NGC 4631
  | access-date=2006-08-22}}</ref>  Because this nearby galaxy is seen edge-on from [[Astronomy:Earth|Earth]], professional astronomers observe this galaxy to better understand the gas and stars located outside the plane of the galaxy.

== Starburst and superwind ==
[[File:NGC 4631 Hubble mosaic.jpg|thumb|left|300px|NGC 4631 mosaic of two [[Astronomy:Hubble Space Telescope|HST]] images; 7.2′x2′ view]]
NGC 4631 contains a central starburst, which is a region of intense [[Astronomy:Star formation|star formation]].  The strong star formation is evident in the emission from [[Physics:Ion|ion]]ized [[Chemistry:Hydrogen|hydrogen]]<ref name="randetal1992">{{cite journal
  | author=R. J. Rand | author2=S. R. Kulkarni | author3=J. J. Hester
  | title=Warm ionized gas in the edge-on galaxies NGC 4565 and NGC 4631
  | journal=Astrophysical Journal
  | date=1992
  | volume=396
  | pages=97–103
  | bibcode=1992ApJ...396...97R  | doi=10.1086/171699
| doi-access=free
  }}</ref> and interstellar dust heated by the stars formed in the starburst.<ref name="bendoetal2006">{{cite journal
  | author=G. J. Bendo | display-authors= 4 | author2= D. A. Dale | author3= B. T. Draine | author4= C. W. Engelbracht | author5= R. C. Kennicutt, Jr. | author6=D. Calzetti | author7=K. D. Gordon | author8=G. Helou | author9=D. Hollenbach | author10=A. Li | author11=E. J. Murphy | author12=M. K. M. Prescott | author13=J.-D. T. Smith
  | title=The Spectral Energy Distribution of Dust Emission in the Edge-on Spiral Galaxy NGC 4631 as Seen with Spitzer and the James Clerk Maxwell Telescope
  | journal=Astrophysical Journal
  | date=2006
  | volume=652
  | issue=1
  | pages=283–305
  | bibcode=2006ApJ...652..283B  | doi=10.1086/508057
|arxiv = astro-ph/0607669 | s2cid= 119419587 }}</ref>  The most massive stars that form in star formation regions only burn hydrogen gas through [[Physics:Nuclear fusion|fusion]] for a short period of time, after which they explode as supernovae.  So many supernovae have exploded in the center of NGC 4631 that they are blowing gas out of the plane of the galaxy. This [[Astronomy:Galactic superwind|superwind]] can be seen in [[Physics:X-ray|X-ray]]s<ref name="wangetal1994">{{cite journal
  | author=Q. D. Wang | display-authors=4 | author2=R. A. S. Walterbos | author3=M. F. Steakley | author4=C. A. Norman | author5= R. Braun
  | title=ROSAT detection of diffuse hot gas in the edge-on galaxy NGC 4631
  | journal=Astrophysical Journal
  | date=1994
  | volume=439
  | pages=176–184
  | bibcode=1995ApJ...439..176W
  | doi=10.1086/175162| hdl=2060/19950011081 | s2cid=121407361 | hdl-access=free}}</ref> and in [[Physics:Spectral line|spectral line]] emission.<ref name="randetal1992" />  The gas from this superwind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.<ref name="wangetal1">{{cite journal
  | author=Q. D. Wang | display-authors= 4 | author2= S. Immler | author3= R. Walterbos | author4= J. T. Lauroesch | author5= D. Breitschwerdt
  | title=Chandra Detection of a Hot Gaseous Corona around the Edge-on Galaxy NGC 4631
  | journal=Astrophysical Journal
  | date=2001
  | volume=555
  | issue=2
  | pages=L99–L102
  | bibcode=2001ApJ...555L..99W  | doi=10.1086/323179
|arxiv = astro-ph/0105541 | s2cid= 15558867 }}</ref>

Although no [[Astronomy:Supernova|supernova]]e have been observed in NGC 4631 yet, a [[Astronomy:Luminous red nova|luminous red nova]], designated AT 2021biy, was discovered on 29 January 2021 (type LRN, mag. 18.1).<ref>[https://www.wis-tns.org/object/2021biy Transient Name Server entry for AT 2021biy.] Retrieved 10 November 2023.</ref>

== Nearby galaxies and galaxy group ==
NGC 4631 has a nearby companion [[Astronomy:Dwarf elliptical galaxy|dwarf elliptical galaxy]], [[Astronomy:NGC 4627|NGC 4627]].  NGC 4627 and NGC 4631 together were listed in the ''[[Astronomy:Atlas of Peculiar Galaxies|Atlas of Peculiar Galaxies]]'' as an example of a "double galaxy" or a galaxy pair.<ref name="arp1966">{{cite journal
  | author=H. Arp
  | title=Atlas of Peculiar Galaxies
  | journal=Astrophysical Journal Supplement
  | date=1966
  | volume=14
  | pages=1–20
  | bibcode=1966ApJS...14....1A  | doi=10.1086/190147
}}</ref>

NGC 4631 and NGC 4627 are part of the [[Astronomy:NGC 4631 Group|NGC 4631 Group]], a group of galaxies that also includes the interacting galaxies [[Astronomy:NGC 4656|NGC 4656]] and [[Astronomy:NGC 4657|NGC 4657]].<ref name="nbg">{{cite book 
  | author=R. B. Tully
  | date=1988
  | title=Nearby Galaxies Catalog
  | publisher=Cambridge University Press
  | location=Cambridge
  | isbn=978-0-521-35299-4}}</ref><ref name="fouqueetal1992">{{cite journal
  | author=P. Fouque | author2=E. Gourgoulhon | author3=P. Chamaraux | author4=G. Paturel
  | title=Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members
  | journal=Astronomy and Astrophysics Supplement
  | date=1992
  | volume=93
  | pages=211–233
  | bibcode=1992A&AS...93..211F}}</ref><ref name="garcia1993">{{cite journal
  | author=A. M. Garcia
  | title=General study of group membership. II - Determination of nearby groups
  | journal=Astronomy and Astrophysics Supplement
  | date=1993
  | volume=100
  | pages=47–90
  | bibcode=1993A&AS..100...47G}}</ref><ref name="giuricinetal2002">{{cite journal
  | author=G. Giuricin | author2=C. Marinoni | author3= L. Ceriani | author4= A. Pisani
  | title=Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
  | journal=Astrophysical Journal
  | date=2000
  | volume=543
  | issue=1
  | pages=178–194
  | bibcode=2000ApJ...543..178G  | doi=10.1086/317070
|arxiv = astro-ph/0001140 | s2cid=9618325 }}</ref>  However, exact group identification is problematic because this galaxy and others lie in a part of the sky that is relatively crowded.  Estimates of the number of galaxies in this group range from 5<ref name="nbg" /> to 27,<ref name="giuricinetal2002" /> and all studies identify very different member galaxies for this group.

{{clear left}}

== See also ==
*[[Astronomy:NGC 891|NGC 891]], a similar edge-on spiral galaxy
*[[Astronomy:NGC 4565|NGC 4565]], a similar edge-on spiral galaxy
*[[Astronomy:NGC 5907|NGC 5907]], a similar edge-on spiral galaxy

== References ==
{{reflist}}

== External links ==
*[http://antwrp.gsfc.nasa.gov/apod/ap040123.html APOD (2004-01-23)] – The Whale Galaxy
*[http://apod.nasa.gov/apod/ap100517.html APOD (2010-05-17)] – The Whale Galaxy (a better image)
*{{WikiSky}}
*{{CelestialRefEx|siblings=show}}
* [http://messier.seds.org/xtra/ngc/n4631.html SEDS] – NGC 4631

{{Sky|12|42|08|+|32|32|29|30000000}}
{{Catalogs|NGC=4631|UGC=7865|PGC=42637|Arp=281|C=32}}
{{Caldwell catalogue}}

{{DEFAULTSORT:NGC 4631}}
[[Category:Barred spiral galaxies]]
[[Category:NGC 4631 Group]]
[[Category:Canes Venatici]]
[[Category:NGC objects|4631]]
[[Category:UGC objects|07865]]
[[Category:Principal Galaxies Catalogue objects|42637]]
[[Category:Arp objects|281]]
[[Category:Caldwell objects|032b]]

{{Sourceattribution|NGC 4631}}