Sky and Telescope - January 2016 - 64

Gargantuan Galaxies

ν
ERIDANUS

- 4°

1350
- 34°

FORNAX

1380

1612
1613

1404
1607

1386

1601

1627
1621

1374

ERIDANUS

IC 373

1365

r1
r3

1606
1603

1326
1317

1580

5
6
7
8
9
10

1379
1387

- 36°

1599

1628

1399

1427

1611

1609

- 5°

5
6
7
8
9
10

Star magnitudes

1625

1618
Star magnitudes

1622

1600

Fornax A
(1316)

1604
- 38°
1594
4h 35m

4h 30m

3h 50m

bright, round 10th-magnitude haze about 4′ across with
a dense, stellar core. NGC 1400 shines a bit fainter as an
11th-magnitude, slightly oval spot about 12′ southwest
of NGC 1407. With a larger scope and/or darker skies,
a number of other fainter systems in this cluster also
become viable observing targets.
NGC 1199 is the brightest member of Hickson
Compact Group (HCG) 22, located about 2° northeast of
Tau1 (1 Eridani). To get there, it's easiest to follow a nice
dipper-like asterism of 7th-magnitude stars. Just oﬀ the
end of the dipper are HCG 22 and NGC 1199. Classiﬁed as an E3, this galaxy's degree of ﬂattening is a bit
more noticeable than with NGC 1400 or NGC 1407. In
my 13.1-inch Dobsonian, NGC 1199 appears as an oval
measuring 2′ × 1.5′ with a bright core, oriented roughly
northeast-southwest. Make sure to check out the other
fainter cluster members as well. About 35′ to the east of
NGC 1199 lies NGC 1209, a strongly elongated E6 galaxy.
It's been described as "disky," as images reveal a hint of
an equatorial disk. In my 11-inch Schmidt-Cassegrain at
155×, it appears as a moderately faint 1.5′ × 1′ oval haze
oriented east-west.
A classic example of a "boxy" elliptical lies in the
northeast corner of Eridanus, near the Orion border,
about 2° southwest of Nu (ν) Eridani. A nice chain of
6th- to 8th-magnitude stars leads from Nu to NGC 1600,
an impressive system even for one of these monsters.
Though at a distance of about 209 million light-years,
this trillion-solar-mass E3-E4 galaxy shines at magnitude
10.9 and is at least 3 magnitudes brighter than the surrounding galaxies. Visually, it's a 2′ × 1.5′ oval oriented
nearly north-south, with a moderately concentrated core
and surrounded by several much fainter systems.
Outsize ellipticals like NGC 1600 are extremely rare
64

Januar y 2016 sky & telescope

3h 40m

3h 30m

and generally found in the cores of rich galaxy clusters.
These massive supergiants are sometimes called cD (for
"central diﬀuse") galaxies as they are often embedded in
faint, diﬀuse halos than can exceed a million light-years
in radius. These giants are thought to be the product of
"galactic cannibalism," a gravitational merger between
two or more galaxies. Many of the resultant galaxies sport
multiple nuclei, vast numbers of globular clusters, and
other physical remnants of these violent encounters.
Winter skies hold a few good examples of this rare
class of galaxy; they're relatively low in the south when
they transit the meridian, but still within reach of
observers in mid-northern latitudes. For example, in the
core of the Fornax Galaxy Cluster lies a spectacular pair
of giant ellipticals, NGC 1399 and NGC 1404. Finding
this pair of galaxies isn't diﬃcult: ﬁrst locate the bright
triangle of stars - g, f, and h Eridani - then sweep
about 2° west from the northernmost star (g). NGC 1399
is a classic cD galaxy, displaying a huge diﬀ use halo
with upwards of 7,000 globular clusters in orbit. It's the
second brightest galaxy in the cluster at magnitude 9.6.
Slightly smaller and dimmer NGC 1404 lies a mere 8′ to
the southeast. In my 13.1-inch scope at 150×, both appear
as bright, round, diﬀ use spots about 3′ across with
condensed cores. NGC 1399 also shows a faint ﬁeld star
just north of the nucleus, leading to the impression of a
"supernova" or double nuclei.
Much better placed for northern observers is the
exotic NGC 1275, also known as Perseus A. Located in
the heart of the Perseus Cluster, this cD giant harbors an
active galactic nucleus (AGN) typical of a type 1.5 Seyfert
galaxy. Superimposed on NGC 1275 (from our point of
view) is a smaller spiral galaxy, or "high-velocity system,"
that's being torn apart as it dashes "headlong" towards

Sky and Telescope - January 2016

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