NGC 21

{{short description|Galaxy in the constellation Andromeda}}

{{Infobox galaxy

| name = NGC 21

| image = File:NGC29 - SDSS DR14.jpg

| caption = NGC 21/NGC 29 (Sloan Digital Sky Survey)

| epoch = J 2000.0

| constellation name = Andromeda

| ra = {{RA|00|10|46.9}}

| dec = {{DEC|+33|21|10}}

| z = 0.015911{{cite web

|title=NASA/IPAC Extragalactic Database

|work=Results for NGC 0021

|url=http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC+21&img_stamp=yes&extend=no

|access-date=2010-05-03}}

| h_radial_v = {{nowrap|4770 ± 4 km/s}}

| dist_ly = 234 ± 29 Mly
{{nowrap|(71.7 ± 8.9 Mpc)}}{{cite web

|title=Distance Results for NGC 0021

|work=NASA/IPAC Extragalactic Database

|url=http://nedwww.ipac.caltech.edu/cgi-bin/nDistance?name=NGC+0021

|access-date=2010-05-03}}

| type = SAB(s)bc

| appmag_v = +12.8

| absmag_v = -20.75{{Cite web|url=https://in-the-sky.org/data/object.php?id=NGC21|title = The galaxy NGC 21}}

| size_v = 1,2′ × 0,59′

| notes =

| names = {{odlist | IRAS= 00082+3304 | MCG= +05-01-048 | CGCG= 499-066 | NGC= 29 | UGC= 100 | PGC= 767}}

}}

NGC 21 (also known as NGC 29) is a spiral galaxy in the Andromeda constellation. It was discovered by German-British astronomer William Herschel on 26 November 1790. Lewis Swift observed it again in 1885, leading to its double listing in the New General Catalogue.