NGC 157 is an intermediatespiral galaxy in the constellation ofCetus, positioned about 4° east of the starIota Ceti. This galaxy can be viewed from suburban skies using a moderate-sized telescope.[5] It was discovered on December 13, 1783 byWilliam Herschel. The compiler of theNew General Catalogue,John Louis Emil Dreyer noted that NGC 157 was "pretty bright, large, extended, between 2 considerably bright stars".[7] It is a relatively isolated galaxy; the nearest other galaxy of comparable luminosity lies at a separation of 4.2 Mly (1.3 Mpc).[8]
NGC 157 from the Mount Lemmon SkyCenter using the 0.8m Schulman Telescope
Themorphological classification of NGC 157 is SAB(rs)bc,[6] indicating this is a weakly-barred spiral galaxy (SAB) with a transitional ring structure (rs) and moderate to loosely-wound arms (bc). The plane of the galaxy is inclined at an angle of 61.8° to the line of sight from the Earth.[6] It has symmetric arms that becomeflocculent in the outer parts, breaking into multiple arms. The rotation curve for this galaxy undergoes a sharp decline, suggesting a low mass or a small dark matter halo.[8] It is considered a quiescent galaxy, showing littlestar formation activity.[9] However, there is astarburst region in the nucleus forming new stars at the rate of about onesolar mass per year.[10]
This galaxy has been host to two observedsupernova events.
SN 2009em was discovered byBerto Monard [it] on 5 May 2009, about 34″ west and 10″ south of the galaxy core.[11] It was determined to be aType Ic supernova.[12]
SN 2022jli (Type Ic, mag. 14.4) was discovered by Berto Monard on 5 May 2022.[13]
^Sempere, M. J.; Rozas, M. (January 1997). "Dynamical model of the grand-design spiral galaxy NGC 157".Astronomy and Astrophysics.317:405–415.Bibcode:1997A&A...317..405S.
Media related toNGC 157 at Wikimedia Commons
