| Quoted from SEDS
Discovered by John Flamsteed about 1690.
The Rosetta Nebula is a vast cloud of dust and gas, extending over an
area of more than 1 degree across, or about 5 times the area covered by
the full moon. Its parts have been assigned different NGC numbers: 2237,
2238, 2239, and 2246. Within the nebula, open star cluster NGC 2244 is
situated, consisted of the young stars which recently formed from the
nebula's material, and the brightest of which make the nebula shine by
exciting its atoms to emit radiation. Star formation is still in
progress in this vast cloud of interstellar matter; a recent finding of
a very young star with a Herbig-Haro type jet by astronomers at the NOAO
has been announced in
Press
Release NOAO 04-03 on January 22, 2004.
Although various values for its distance occur in the literature, our
adopted distance from the Sky Catalog 2000 implies a true diameter of
the nebula of about 130 light years. Burnham quotes a mass estimation of
10,000 (Minkowski 1949) to 11,000 (Menon 1962) solar masses, so it is
one of the more massive diffuse nebulae.
Open cluster NGC 2244 was discovered by Flamsteed about 1690. The
nebula, however, was not even seen by William Herschel (who found the
cluster); its different parts were discovered only by John Herschel (NGC
2239 = GC 1420 = h 392), Marth (NGC 2238 = GC 5361 = Marth 99), and
Swift (NGCs 2237 and 2246); note that while now these numbers are used
for describing parts of the diffuse nebula, their original NGC
description is quite different:
2237 pretty bright, very very large, diffuse (?= [GC] 5361 [= NGC 2238])
2238 small [faint] star in nebulosity
2239 star of mag 8 in large, poor, bright cluster
2246 extremely faint, large, irregularly round, extremely difficult
Nevertheless, the nebula is a splendid object, especially for
astrophotography.
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