Sky and Telescope - November 2017 - 57

NGC 7741

NGC 7741 takes magnification well, revealing a wealth of detail with closer scrutiny.
The author completed this sketch with her
15-inch reflector at 216×.

NGC 7741: A DA M BLOCK / M OUN T LEM M ON SK YCEN TER / UNIV ERSIT Y OF A RIZON A; SK E TCH: SUE FRENCH

p NGC 7741 is a moderately bright face-on barred spiral, pinned at the north-northwest edge by a 10th-magnitude star. The central bar offers a
strong brightening that runs east-west across the galaxy's center.

one of the most massive spiral galaxies
known, weighing in at 600 billion solar
masses, as well as one of the fastestspinning with a maximum rotational
velocity of about 300 miles per second.
This is another far-ﬂung galaxy, 290
million light-years distant.
Our next goal is the face-on, barred
spiral galaxy NGC 7741. There are no
bright stars near enough to serve as a
good guide, but if your telescope has an
equatorial mount, you can drop 3.3°
due south from the 5th-magnitude
yellow-orange star 78 Pegasi. NGC 7741
is by far the brightest galaxy in the area.
At 68× my 10-inch scope exposes the
bar, which is this galaxy's most obvious
feature. The bar is tipped south of east

and points toward a 12th-magnitude
star 3′ away. A golden, 10th-magnitude
star perches 2′ north-northwest of the
bar's center. At 115× this star gains a
fainter companion to its south-southeast, while the bar grows a 2½′ halo that
extends farther south than north.
NGC 7741 is a pretty galaxy
through the 15-inch scope. At 102×
the bar stands out quite well and grows
brighter toward the center, and the
halo stretches as far as the dimmer
star of the north-northwestern pair.
At a magniﬁcation of 216×, tantalizing
details unfold. The eastern end of the
bar hooks north, while the western end
hooks south, and extending from each
hook the sides of the galaxy are brighter.

Galaxies in the Great Square of Pegasus
Object
NGC 7678

Surface
Brightness

Mag(v)

Size/Sep

Dec.

13.2

11.8

2.2′ × 1.7′

23h 28.5m

+22° 25′

20.9m

+25° 54′

NGC 7628

12.7

1.1′ × 0.9′

23h

UGC 12515

13.1

12.9

1.4′ × 1.1′

23h 19.9m

+26° 16′

25.4m

+28° 30′
+26° 05′

UGC 12591

12.8

12.9

1.7′ × 0.7′

23h

NGC 7741

14.0

11.3

4.4′ × 3.0′

23h 43.9m

Angular sizes and separations 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.

Overall, the halo is tilted north-northeast. I estimate a size of about 3¼′ × 1¼′,
but the galaxy is rather insubstantial at
the tips, so it's difﬁcult to be precise.
According to The de Vaucouleurs Atlas
of Galaxies (Buta, Corwin, and Odewahn, 2007), NGC 7741 can be considered a prototype of the SB(s)cd morphological type. This can be decoded as:
spiral galaxy (S); spiral arms sprout from
the ends of a bar (B(s)); little or no bulge
and very open arms showing widespread
resolution into large knots (cd).
From its apparent size, you might
suspect that NGC 7741 is the closest
galaxy in our tour, and you'd be correct.
In fact, it's too close to us for redshift to
give an accurate measure of its distance.
The mean redshift-independent distance given in the NASA/IPAC Extragalactic Database (NED) is 46 million
light-years. The surrounding ﬁeld is
liberally dosed with background galaxies. Intriguingly, very deep color images
show one of them shining right through
the galaxy's translucent façade.
On your next clear night, see if you
can round up some of these challenging
Square galaxies.
¢ Contributing Editor SUE FRENCH enjoys perusing the skies of upstate New
York with her husband Alan, a long-time
amateur telescope maker.
s k y a n d t e l e s c o p e . c o m * N O V E M B E R 2 0 17

http://www.skyandtelescope.com

Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017