NGC 157

NGC 157
VLT image of NGC 157
Observation data (J2000 epoch)
ConstellationCetus
Right ascension00h 34m 46.751s[1]
Declination−08° 23′ 47.36″[1]
Redshift0.0055[2]
Heliocentric radial velocity1651 km/s[3]
Distance39.4 Mly (12.1 Mpc)[3]
75 Mly (23 Mpc)[4]
Apparent magnitude (V)10.4[5]
Apparent magnitude (B)11.07[3]
Characteristics
TypeSAB(rs)bc[6]
Size90 kly[7]
Apparent size (V)4.0′ × 2.4′[5]
Other designations
MCG -02-02-056, PGC 2081, 2MASSX J00344675-0823473[2]
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NGC 157 is an intermediate spiral galaxy in the constellation of Cetus, positioned about 4° east of the star Iota Ceti. This galaxy can be viewed from suburban skies using a moderate-sized telescope.[5] It was discovered on December 13, 1783 by William Herschel. The compiler of the New 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

The morphological 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 become flocculent 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 little star formation activity.[9] However, there is a starburst region in the nucleus forming new stars at the rate of about one solar mass per year.[10]

This galaxy has been host to two observed supernova events. The first, 2009em, was discovered 5 May 2009, about 34″ west and 10″ south of the galaxy core.[11] It was determined to be a Type Ic supernova.[12] On 5 May 2022, Type Ic supernova event SN 2022jli was observed in NGC 157, reaching a peak magnitude of 14.4.[13]

  1. ^ a b Cite error: The named reference 2MASS was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference simbad was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Tully_et_al_2016 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Moore_et_al_2023 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference O'Meara_2007 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Crowther_2013 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference cseligman was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Zobnina_Zasov_2020 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Zhu_et_l_2009 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Sempere_Rozas_1997 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Monard_2009 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Navasardyan_Benetti_2009 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference TNS_2023 was invoked but never defined (see the help page).