NGC 4242

{{Short description|Galaxy in constellation Canes Venatici}}

{{Infobox galaxy

| name = NGC 4242

| image = 280px

| caption = NGC 4242 imaged by the Hubble Space Telescope

| epoch = J2000

| constellation name = Canes Venatici

| ra = {{RA|12|17|30.174}}{{cite journal|title=VizieR Online Data Catalog: The SDSS Photometric Catalog, Release 7|author=Adelman-McCarthy, J. K.|display-authors=etal|journal=VizieR On-line Data Catalog|date=2009|bibcode=2009yCat.2294....0A}}

| dec = {{DEC|+45|37|09.46}}

| z = 0.00176

| h_radial_v = 527 km/s

| dist_ly = {{cvt|5.45|±|0.20|Mpc|Mly|order=flip|lk=on}}{{cite journal|title=Cosmicflows-2: The Data|author1=Tully, R. Brent|display-authors=etal|journal=The Astronomical Journal|volume=146|issue=4|pages=86|date=2013|bibcode=2013AJ....146...86T|doi=10.1088/0004-6256/146/4/86|arxiv=1307.7213|s2cid=118494842}}

| −7.3{{cite journal|bibcode=2012MNRAS.419.1362Y|title=HST/WFPC2 Imaging of the Dwarf Satellites And XI and And XIII : HB Morphology and RR Lyraes|journal=Monthly Notices of the Royal Astronomical Society|volume=419|issue=2|pages=1362|doi=10.1111/j.1365-2966.2011.19792.x|year=2012|last1=Yang|first1=S.-C|last2=Sarajedini|first2=A|doi-access=free |arxiv=1109.2038|s2cid=119190619}}

| type = SABdm{{cite journal|bibcode=2015ApJS..217...27A|arxiv=1502.03545|doi=10.1088/0067-0049/217/2/27|title=A Catalog of Visually Classified Galaxies in the Local (z ∼ 0.01) Universe|journal=The Astrophysical Journal Supplement Series|volume=217|issue=2|pages=27|year=2015|last1=Ann|first1=H. B|last2=Seo|first2=Mira|last3=Ha|first3=D. K|s2cid=119253507}}

| group_cluster = Canes II Group

| mass =

| size =

| appmag_v = 11.37

| appmag_b = 10.83

| absmag_v =

| size_v = 5.0′ × 0.38′{{cite journal|bibcode=2007ApJS..173..185G|display-authors=1|arxiv=astro-ph/0606440|doi=10.1086/516636|title=The GALEX Ultraviolet Atlas of Nearby Galaxies|journal=The Astrophysical Journal Supplement Series|volume=173|issue=2|pages=185–255|year=2007|last1=Gil De Paz|first1=Armando|last2=Boissier|first2=Samuel|last3=Madore|first3=Barry F|last4=Seibert|first4=Mark|last5=Joe|first5=Young H|last6=Boselli|first6=Alessandro|last7=Wyder|first7=Ted K|last8=Thilker|first8=David|last9=Bianchi|first9=Luciana|last10=Rey|first10=Soo-Chang|last11=Rich|first11=R. Michael|last12=Barlow|first12=Tom A|last13=Conrow|first13=Tim|last14=Forster|first14=Karl|last15=Friedman|first15=Peter G|last16=Martin|first16=D. Christopher|last17=Morrissey|first17=Patrick|last18=Neff|first18=Susan G|last19=Schiminovich|first19=David|last20=Small|first20=Todd|last21=Donas|first21=Jose|last22=Heckman|first22=Timothy M|last23=Lee|first23=Young-Wook|last24=Milliard|first24=Bruno|last25=Szalay|first25=Alex S|last26=Yi|first26=Sukyoung|s2cid=119085482}}

| names = {{odlist|NGC=4242|UGC=7323|MCG=+08-22-098|PGC=39423}}{{cite simbad|title=NGC 4242|access-date=14 April 2018}}

}}

NGC 4242 is a spiral galaxy in the northern constellation of Canes Venatici. The galaxy is about 18 million light years (5.5 megaparsecs) away. It was discovered on 10 April 1788 by William Herschel,{{cite web|url=http://cseligman.com/text/atlas/ngc42.htm#4242|title=New General Catalogue objects: NGC 4200 - 4249|author=Seligman, Courtney|website=cseligman.com|access-date=10 April 2018}} and it was described as "very faint, considerably large, irregular, round, very gradually brighter in the middle, resolvable" by John Louis Emil Dreyer, the compiler of the New General Catalogue.{{cite web|url=http://spider.seds.org/ngc/ngc.cgi?NGC+4242|title=Revised NGC Data for NGC 4242 - Hartmut Frommert - SEDS|website=seds.org|access-date=14 April 2018}}

NGC 4242's galaxy morphological type is SABdm. This means that it is an intermediate spiral galaxy, with loosely wound spiral arms and is generally irregular in appearance. It was photographed by the Hubble Space Telescope in 2017. The image shows an asymmetric center and a small galactic bar. NGC 4242 has a relatively low surface brightness and rate of star formation.{{cite web|url=http://www.spacetelescope.org/images/potw1729a/|title=Dim and diffuse | ESA/Hubble|website=www.spacetelescope.org|date=2017|access-date=14 March 2018}} NGC 4242 may be a satellite galaxy of Messier 106{{cite journal|bibcode=2014ApJ...788..146S|doi=10.1088/0004-637X/788/2/146|arxiv=1404.7222|title=A Survey of Satellite Galaxies Around Ngc 4258|journal=The Astrophysical Journal|volume=788|issue=2|pages=146|year=2014|last1=Spencer|first1=Meghin|last2=Loebman|first2=Sarah|last3=Yoachim|first3=Peter|s2cid=118622457}} and is a member of the Canes II Group.{{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}}{{Cite web|url=http://www.atlasoftheuniverse.com/galgrps/cvnii.html|title=The Canes II Group|website=www.atlasoftheuniverse.com|access-date=2018-04-16}}

SN 2002bu was detected in NGC 4242, brightening to its peak magnitude of 15.5 in 2002.{{cite simbad|title=SN 2002bu|access-date=14 April 2018}} It was originally classified as a type II supernova. In 2011, it was thought to be a supernova impostor like SN 2008S,{{cite journal | bibcode=2011MNRAS.415..773S | doi=10.1111/j.1365-2966.2011.18763.x | arxiv=1010.3718 | title=Luminous blue variable eruptions and related transients: Diversity of progenitors and outburst properties | journal=Monthly Notices of the Royal Astronomical Society | volume=415 | issue=1 | pages=773–810 | year=2011 | last1=Smith | first1=Nathan | last2=Li | first2=Weidong | last3=Silverman | first3=Jeffrey M|last4=Ganeshalingam | first4=Mohan | last5=Filippenko | first5=Alexei V | doi-access=free | s2cid=85440811}} and in 2021 researchers reclassified it as a gap transient.{{cite journal | arxiv=2107.02179| doi=10.1093/mnras/stab1938| doi-access=free| title=A systematic reclassification of Type IIn supernovae| date=2021| last1=Ransome| first1=C. L.| last2=Habergham-Mawson| first2=S. M.| last3=Darnley| first3=M. J.| last4=James| first4=P. A.| last5=Filippenko| first5=A. V.| last6=Schlegel| first6=E. M.| journal=Monthly Notices of the Royal Astronomical Society| volume=506| issue=4| pages=4715–4734}}{{cite web | website=Transient Name Server | title=SN{{nbsp}}2002bu | url=https://www.wis-tns.org/object/2002bu | publisher = IAU | access-date=31 August 2024}}