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Форум » Досуг » Космос » NGC 22
NGC 22
ingvarr
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NGC 22 (другие обозначения — UGC 86, MCG 5-1-39, ZWG 499.55, PGC 690) — спиральная галактика (Sb) в созвездии Пегас.
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NGC 22 (= PGC 690)
Almost certainly not observed by William Herschel
Almost certainly 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 defined as JH 4, and GC 12 was defined as JH 5 and assumed equal to WH IV 15; and since Dreyer published the NGC it has been assumed that GC 12 = GC 8 = NGC 16. However, in 2014 it was 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 almost certainly wrong, so this note serves as a warning to be wary of 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, a straightforward calculation indicates that NGC 22 is about 385 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 1.55 by 0.95 arcmin, the galaxy is about 170 thousand light years across.

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