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Page last updated Aug 12, 2017

NGC 22 (= PGC 690)
Not observed by William Herschel
Not observed by John Herschel
Discovered (Oct 2, 1883) by Édouard Stephan
A magnitude 13.6 spiral galaxy (type Sb?) in Andromeda (RA 00 09 48.2, Dec +27 49 56)
Historical Identification: Per Dreyer, NGC 22 (Stephan list XIII (#1), 1860 RA 00 02 36, NPD 62 56.9) is "very faint, pretty small, round, a little brighter middle, mottled but not resolved". The position precesses to RA 00 09 48.9, Dec +27 49 52, within 0.2 arcmin of the center of the galaxy listed above and well within its outline, so the identification is certain.
Discovery Notes: When John Herschel published his General Catalog, GC 8 was listed as JH 4 and GC 12 was listed as JH 5 and WH IV 15; and since Dreyer published the NGC it has been assumed that GC 12 = GC 8 = NGC 16 (as discussed in detail in the entry for NGC 16). However, in 2014 Steinicke suggested that JH 5 and WH IV 15 are not observations of NGC 16, but of some faint star or perhaps even NGC 22. As discussed in the entry for NGC 16 that is incorrect, so this note serves as a warning to ignore any suggestion that the Herschels had anything to do with the discovery of NGC 22.
Physical Information: Based on a recessional velocity of 8310 km/sec (and H0 = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 22 is about 385 to 390 million light years away, in good agreement with redshift-independent distance estimates of 335 to 435 million light years. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 375 million light years away at the time the light by which we see it was emitted, about 380 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of about 1.6 by 1.0 arcmin (from the images below), the galaxy is about 175 thousand light years across.
SDSS image of region near spiral galaxy NGC 22
Above, a 12 arcmin wide SDSS image centered on NGC 22
Below, a 2.0 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 22
Below, a 12 arcmin wide SDSS image centered on NGC 22, also showing PGC 212478 and 1820266
SDSS image of region near spiral galaxy NGC 22, also showing several PGC objects

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IC 5350 - 5386 ← NGC Objects: NGC 1 - 49 → NGC 50 - 99