Sky and Telescope - November 2017 - 56

NOVEMBER 2017 OBSERVING
Deep-Sky Wonders

UGC 12515

p The lenticular galaxy UGC 12515 snugs up
to the variable star W Pegasi. The star, which
has a period of 346 days and a magnitude
range of 7.6 to 13, is dropping in brightness
now, making this the ideal time to turn your
scope toward this ghostly galaxy.

taken with the sight, proclaiming it a
lovely, dimmer version of the Beta (β)
Andromedae/NGC 404 pairing. Mark's
discovery is the lenticular (lens-shaped)
galaxy UGC 12515, which sits 26′
north-northwest of our previous galaxy.
In the 10-inch scope at 166×, UGC
12515 is only a tiny, roundish smudge
seen with averted vision, just south of a
reddish orange star. After familiarizing
myself with the galaxy, I could faintly
see it with direct vision. The galaxy is
easier to see when it's pulled farther
away from the star at 213×. Upping
the magniﬁcation to 299×, it becomes
a small oval leaning northeast. My
15-inch reﬂector at 216× reveals a ½′ ×
1/3′ glow with a broadly brighter center.
Beta Andromedae is known as
Mirach, and the galaxy NGC 404 has
been dubbed the Ghost of Mirach. The
star cuddled up to UGC 12515 is the
Mira-type variable W Pegasi, so perhaps
we could call UGC 12515 the Ghost of
W Pegasi. Since W Peg has a period of
346 days and a magnitude range of 7.6
to 13, sometimes the star takes on a
ghostly pallor itself, too weak to ﬂaunt
its Mirach-like hue. W Peg is fading
now, so the sooner you can observe it,
the better.
56

N O V E M B E R 2 0 17 * S K Y & T E L E S C O P E

In the 15-inch scope, UGC 12591
seems to grow gently brighter toward
the center at 133× and shows an abrupt
drop in brightness along the southsoutheastern ﬂank at 192×. At 216×
I can glimpse a little fuzz beyond the
brightness drop, indicating the presence
of a dark lane. A small, brighter core
rests just above the northern side of the
lane. As judged by comparing the length
of the galaxy to the distance between
the orange star and a 12th-magnitude
star to the east, UGC 12591 appears
roughly 50″ long and half as wide.
The morphology of UGC 12591
is considered an intermediate type
between S0 galaxies (lenticulars with
little or no spiral structure) and Sa
galaxies (spirals with large bulges and
tightly wrapped spiral arms). It's also

UGC 12591

In the eyepiece, UGC 12591 shows as a gauzy, elongated glow with a noticeable uptick
in brightness at its center. It takes a Hubble Space Telescope photograph to reveal this
galaxy's true nature: It's a massive hybrid of a spiral and a lenticular structure with a
rotational speed up to 1.8 million kilometers per hour.

UGC 12515: POSS-II / CA LTECH / STSCI / PA LO M A R OBSERVATORY; UGC 12591: ESA / N ASA / HUBBLE SPACE TELESCOPE

W Pegasi

Despite their apparent similarity
in the sky, UGC 12515 is 340 million
light-years distant, while NGC 7628 is
half as far away. In reality, UGC 12515
is 2.7 times as luminous as NGC 7628.
Mark Stuart also pointed me in the
direction of UGC 12591, which nuzzles
the Great Square's northern border,
1.4° west of the 6th-magnitude star
HD 221394. This UGC galaxy is more
impressive than the last. Although very
small and gauzy at 88× through the
10-inch scope, UGC 12591 is readily visible and holds a brighter center. Standing out better at 187×, this
elongated galaxy bridges about 1′ and
boasts a brighter oval center and a very
tiny, bright nucleus. A 10th-magnitude
orange star hangs 1.3′ south of its westsouthwestern tip.

Sky and Telescope - November 2017

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