NGC 7742

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NGC 7742[1]
Seyfert Galaxy NGC 7742.jpg
A Hubble Space Telescope (HST) image of NGC 7742.
Credit: NASA/ESA/STScI/AURA.
Observation data
Epoch J2000
Constellation Pegasus
Right ascension 23h 44m 15.7s[2]
Declination +10° 46′ 02″[2]
Apparent dimension (V) 1.778 × 1.698 moa[3]
Apparent magnitude (V) 12.35[2]
Characteristics
Type SA(r)b,[2] LINER/HII[2]
Astrometry
Heliocentric radial velocity 1663 ± 1[2] km/s
Redshift 0.005547 ± 0.000003[2]
Galactocentric velocity 1809 ± 6[2] km/s
Distance 72.4 ± 6.2 Mly (22.20 ± 1.90 Mpc)
Other designations
UGC 12760,[2] MCG +02-60-010,[2] UZC J234415.8+104601,[2] 2MASX J23441571+1046015[2]
Database references
SIMBAD Search NGC 7742 data
See also: Galaxy, List of galaxies

NGC 7742 is a face-on unbarred spiral galaxy in the constellation Pegasus. In the Catalogue of Named Galaxies, it is called Diadema Pegasi, or the diadem galaxy.[4]

The galaxy is unusual in that it contains a ring but no bar.[5] Typically, bars are needed to produce a ring structure. The bars' gravitational forces move gas to the ends of the bars, where it forms into the rings seen in many barred spiral galaxies. In this galaxy, however, no bar is present, so this mechanism cannot be used to explain the formation of the ring. O. K. Sil'chenko and A. V. Moiseev proposed that the ring was formed partly as the result of a merger event in which a smaller gas-rich dwarf galaxy collided with NGC 7742. As evidence for this, they point to the unusually bright central region, the presence of highly inclined central gas disk, and the presence of gas that is counterrotating (or rotating in the opposite direction) with respect to the stars.[5]

Two Type II supernovae, SN 1993R and SN 2014cy, have been detected in NGC 7742.[6]

See also[edit]

  • NGC 7217 - a face-on spiral galaxy with identical characteristics
  • Sombrero Galaxy - a similar galaxy with a dust ring

References[edit]

  1. ^ Filho, M. E.; Barthel, P. D.; Ho, L. C. (October 2002). "The Nature of Composite LINER/HII Galaxies, Part II". The Astrophysical Journal Supplement. The University of Chicago Press. 142 (2): 223–238. arXiv:astro-ph/0205196Freely accessible. Bibcode:2002ApJS..142..223F. doi:10.1086/341786. ISSN 0067-0049. 
  2. ^ a b c d e f g h i j k l "NASA/IPAC Extragalactic Database". Results for NGC 7742. Retrieved 2006-08-20. 
  3. ^ "Centre de Données astronomiques de Strasbourg". Results for NGC 7742. Retrieved 2008-07-09. 
  4. ^ Bodifee, Gerard. "Catalogue of One Thousand Named Galaxies" (PDF). Retrieved 21 May 2017. 
  5. ^ a b O. K. Sil'chenko; A. V. Moiseev (2006). "Nature of Nuclear Rings in Unbarred Galaxies: NGC 7742 and NGC 7217". Astronomical Journal. 131 (3): 1366–1346. arXiv:astro-ph/0512431Freely accessible. Bibcode:2006AJ....131.1336S. doi:10.1086/499945. 
  6. ^ "List of Supernovae". IAU Central Bureau for Astronomical Telegrams. Retrieved 13 September 2015. 

External links[edit]

Coordinates: Sky map 23h 44m 15.7s, +10° 46′ 02″