NGC 251

{{Short description|Galaxy in the constellation Pisces}}

{{Sky|00|47|54.0517|+|19|35|48.788}}

{{Infobox galaxy

| name = NGC 251

| image = NGC251 - SDSS DR14.jpg

| caption = SDSS image of NGC 251

| epoch = J2000

| constellation name = Pisces

| ra = {{RA|00|47|54.0517}}{{cite journal |doi=10.1086/498708 |last1=Skrutskie |first1=Michael F. |last2=Cutri |first2=Roc M. |last3=Stiening |first3=Rae |last4=Weinberg |first4=Martin D. |last5=Schneider |first5=Stephen E. |last6=Carpenter |first6=John M. |last7=Beichman |first7=Charles A. |last8=Capps |first8=Richard W. |last9=Chester |first9=Thomas |last10=Elias |first10=Jonathan H. |last11=Huchra |first11=John P. |last12=Liebert |first12=James W. |last13=Lonsdale |first13=Carol J. |last14=Monet |first14=David G. |last15=Price |first15=Stephan |last16=Seitzer |first16=Patrick |last17=Jarrett |first17=Thomas H. |last18=Kirkpatrick |first18=J. Davy |last19=Gizis |first19=John E. |last20=Howard |first20=Elizabeth V. |last21=Evans |first21=Tracey E. |last22=Fowler |first22=John W. |last23=Fullmer |first23=Linda |last24=Hurt |first24=Robert L. |last25=Light |first25=Robert M. |last26=Kopan |first26=Eugene L. |last27=Marsh |first27=Kenneth A. |last28=McCallon |first28=Howard L. |last29=Tam |first29=Robert |last30=Van Dyk |first30=Schuyler D. |last31=Wheelock |first31=Sherry L. |title=The Two Micron All Sky Survey (2MASS) |journal=The Astronomical Journal |date=1 February 2006 |volume=131 |issue=2 |pages=1163–1183 |bibcode=2006AJ....131.1163S |s2cid=18913331 |issn=0004-6256 |doi-access=free }}

| dec = {{DEC|+19|35|48.788}}

| z = 0.015184{{cite web|url=http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC+251&extend=no&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES|title=NED results for object NGC 0251|publisher=National Aeronautics and Space Administration / Infrared Processing and Analysis Center|access-date=5 May 2017}}

| h_radial_v = 4556 km/s

| dist_ly = {{cvt|62.657|+/-|3.876|Mpc|Mly|lk=on|order=flip}}

| group_cluster =

| type = Sc

| size = {{cvt|45780|pc|ly|lk=on|order=flip}}POSS1 103a-O values used.

| appmag_v =

| appmag_b = 14.6{{cite simbad|title=NGC 251|access-date=5 May 2017}}

| size_v = 2.4{{prime}} × 1.9{{prime}}

| notes =

| names = {{odlist | CGCG= 458-005 | UGC= 490 | MGC=- +03-03-003 | PGC= 2806 | name= KPG 015B}}

}}

NGC 251 is a spiral galaxy in the constellation of Pisces. Its velocity with respect to the cosmic microwave background for is {{val|4224|23|u=km/s|fmt=commas}}, which corresponds to a Hubble distance of {{convert|62.30 ± 4.37|Mpc|Mly|abbr=on|lk=on|order=flip}}.{{r|ned}} Additionally, six non redshift measurements give a distance of {{convert|62.950 ± 1.699|Mpc|Mly|abbr=on|lk=on|order=flip}}.{{cite web | url = https://ned.ipac.caltech.edu/cgi-bin/nDistance?name=NGC+251 | title = Distance Results for NGC 251 | website = NASA/IPAC EXTRAGALACTIC DATABASE | publisher = NASA | access-date = 9 April 2025}} It was discovered on October 15, 1784, by German-British astronomer William Herschel.{{cite web | url = https://cseligman.com/text/atlas/ngc2a.htm#251 | title = New General Catalogue Objects: NGC{{nbsp}}251 | last = Seligman | first = Courtney | website = Celestial Atlas | access-date = 9 April 2025 }}

According to I.D. Karachentsev, NGC 251 forms an isolated galaxy pair with UGC 477.{{cite journal

| last = Karachentsev

| first = I. D.

| title = Catalogue of isolated pairs of galaxies in the northern hemisphere

| journal = Soobshcheniya Spetsial'noj Astrofizicheskoj Observatorii

| volume = 7

| pages = 1-92

| year = 1972

| bibcode = 1972SoSAO...7....1K

}}

One supernova has been observed in NGC 251: SN 2023rky (type II, mag. 18.6) was discovered by the Zwicky Transient Facility on 6 September 2023.{{cite web | website=Transient Name Server | title=SN{{nbsp}}2023rky | url=https://www.wis-tns.org/object/2023rky | publisher = IAU | access-date=9 April 2025}}