Sky and Telescope - November 2018 - 37

NGC 121: N ASA / ESA / HST / STEFA NO CA MPA NI; 47 T UCA N A E: ESO / M.-R. CIONI / VISTA M AG ELL A NIC
CLOUD SURV E Y / CA MBRIDG E ASTRONO MICA L SURV E Y UNIT

integrated magnitude is an impressive 8.0, don't be misled;
the light is spread out over ½° of sky and its anemic surface
brightness, along with a low elevation (declination -34.5°),
conspire to make the Fornax Dwarf a formidable visual target. My only convincing view was from the Southern Hemisphere when the galaxy was high overhead. Even then, I only
noticed a subtle brightening conﬁrmed by tracing around the
galaxy's periphery.
The galaxy itself may be barely detectable, but four of
its ﬁve globulars can be seen through a 10-inch scope (my
comments are based on the view through a 13-inch). John
Herschel found NGC 1049 (Fornax 3), the brightest and most
massive cluster, 103 years prior to Shapley's discovery. He
reported seeing an object "pretty bright; small; round; like a
star 12th magnitude a very little rubbed at the edges, a curious
little object and easily mistaken for a star, which, however, it
certainly is not." That reads pretty close to my own notes at
166×: "moderately bright, small (about 30″ diameter), very
small bright core with a faint halo." Look for this 12.6-magnitude globular 15′ north of 8th-magnitude HD 16690.
While examining additional plates taken from Boyden Station, Shapley also discovered the globular clusters Fornax 2
(visual magnitude 14.1) and Fornax 4 (13.6). Fornax 2 is an
easy 25′ star hop to the southeast of 5.8-magnitude Lambda2
(λ2) Fornacis, but it only appeared as a gauzy 20″ spot of uniform low surface brightness.
Fornax 4 is a strange beast. Although ancient stars dominate the other clusters, Fornax 4 is younger by 2 to 3 billion
years. Furthermore, its central position suggests Fornax 4 may
be the actual core of the Fornax Dwarf, but its radial velocity

and population indicate it's a legitimate globular coincidentally in our line of sight to the center. I noted a hazy 20″ patch
rising suddenly to a small, brighter core.
In the late 1950s Paul Hodge (University of Washington)
added the outer halo globulars Fornax 1 and Fornax 5 using
plates taken in South Africa with the Armagh-DunsinkHarvard (ADH) Baker-Schmidt telescope. Fornax 5 resembles
Fornax 4, with a tight luminous core and a thin fainter halo.
Look for it 13′ west of 7.3-magnitude HD 17060 and 10′
northeast of a string of four stars that point the way to the
globular. With a visual magnitude of 15.6, Fornax 1 is easily
the most challenging of the ﬁve globulars. Good luck!
Legendary observer E. E. Barnard swept up NGC 6822
(Barnard's Galaxy) in 1884 using his 5-inch Byrne refractor.
The galaxy gained fame in 1925 when Edwin Hubble discovered 15 variable stars in it, including 11 Cepheids. Using
Henrietta Leavitt's relationship between the period and luminosity of Cepheids, Hubble announced NGC 6822 as "the
ﬁrst object deﬁnitely assigned to a region outside the galactic
system." Extragalactic astronomy was now ﬁrmly established.
Modern studies place the distance at 1.6 million light-years,
making it an isolated member of the Local Group.
While examining NGC 6822 Hubble also found 10 nebulous objects (ﬁve giant emission nebulae and ﬁve compact
objects) that he labeled with Roman numerals I through X.
He doubted any of these were globulars, but later studies
proved Hubble VII, buried near the center, was a bona ﬁde
16th-magnitude globular with an age of 10 to 11 billion years.
It took a painstaking search in 2010 using my 18-inch
reﬂector in superb conditions just to glimpse Hubble VII as

p BLAZES OF GLORY Left: The only classical globular cluster in the Small Magellanic Cloud, NGC 121 glitters with an abundance of hot, blue stars.
NGC 121 lies about 200,000 light-years from Earth in the direction of the constellation Tucana. Right: Visually, the globular cluster 47 Tucanae appears
to be a close neighbor to NGC 121; only ½º separates the pair in the sky from our point of view. But in fact, with a distance of about 13,500 lightyears, 47 Tucanae is some 15 times closer to us than NGC 121.
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Sky and Telescope - November 2018

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