Sky & Telescope - December 2024 - 58

NGC 2379: GARY IMM; ALL SKETCHES BY IVAN MALY; ALL DSS IMAGES: POSS-II / STSCI / CALTECH /
PALOMAR OBSERVATORY
DECEMBER 2024 OBSERVING
Going Deep by Ivan Maly
Slashes in
the Sky
Spend some time on winter
nights observing flat galaxies.
B
eing able to see complex features,
such as spiral arms in galaxies, is
a rare skill. However, we are hardwired
to detect straight edges. Our eyes are
drawn to them when we point our
telescopes at " flat " galaxies. But even
the famous edge-on Splinter Galaxy,
NGC 5907, still shows something of a
bright bulge in the middle, so you might
be wondering: Are there any galaxies
that are truly flat? Yes! In fact, the Flat
Galaxies Catalogue (FGC) lists more
than 4,000 of these marvels, enough for
a lifetime of exploration.
While studying collective motions
of galaxies in the nearby universe,
Russian astronomer Igor Karachentsev
discovered a relationship between a
galaxy's optical and radio properties
that could be used to derive its distance
independently of redshift. He published
his findings in 1989 in the Astronomical
Journal. The relationship was the
most precise for edge-on galaxies whose
Flat Galaxies
Catalog entry
FGC 2070
FGC 2250
FGC 2255
FGC 2360
FGC 2385
FGC 2379
THIN STREAKS The delicate flat galaxy FGC 2379 lies in the shadow of NGC 7241. Some flat
galaxies not only appear exactly edge-on but also lack any pronounced bulge. They look as if the
sky had been slashed with a fine scalpel.
length on photographic plates was at
least seven times their width - in other
words, flat galaxies. In 1993, Karachentsev
and his colleagues compiled a catalog
hoping it would serve as a source of
targets professional astronomers could
use for measurements that would yield
a wealth of cosmographical information.
Within a decade, however, amateur
astronomers started to dip into the
catalog to pursue its brightest members
as observing targets.
As one might expect reading this
column, " bright " is a relative term
when it comes to the Flat Galaxies
Catalogue. Few of its members exceed
magnitude 14 - the aforementioned
Splinter Galaxy, which is cataloged
as FGC 1875, is one of the brightest
at magnitude 10.3. To get a taste of
the more typical flat galaxies in the
December sky, set up the biggest scope
you have under a dark sky and sample
the starter course below.
UGC designation
UGC 10561
UGC 11435
UGC 11455
UGC 11893
UGC 11994
UGC 11964
Surface Brightness
13.7
13.5
14.4
14.7
13.5
13.1
Mag(v)
14.3
14.2
14.3
15.4
14.0
14.3
Size
RA
2.3′ × 0.3′
2.0′ × 0.3′
2.6′ × 0.5′
2.1′ × 0.3′
2.3′ × 0.3′
1.9′ × 0.2′
16h 46.6m
19h 23.8m
19h 30.0m
22h 04.1m
22h 20.9m
22h 15.5m
Dec.
+62° 49′
+55° 59′
+72° 07′
+33° 56′
+33° 18′
+19° 13′
Angular sizes are from recent catalogs. Visually, an object's size is often smaller than the cataloged value and varies according to the aperture and magnification of
the viewing instrument. Right ascension and declination are for equinox 2000.0.
58 DECEMBER 2024 * SKY & TELESCOPE

Sky & Telescope - December 2024

Table of Contents for the Digital Edition of Sky & Telescope - December 2024