Sky & Telescope - March 2024 - 21

outer halo - likely due to an interaction with the core of the
M81 group about a billion years ago that stripped away the
gas from NGC 2976's outer reaches.
And now we come to our final target of this northerly
quintet and the most challenging of the lot. American astronomer
Edwin Coddington discovered IC 2574 on a photographic
plate captured at Lick Observatory in April 1898, and
in fact today the galaxy is known popularly as Coddington's
Nebula. This 10.4-magnitude dwarf spiral is an elongated
oval with low surface brightness located 3° east of M81. I find
lower magnification works best on this object; for a 10-inch
scope, about 25× should be optimum. Amateur astrophotographer
Stephen Leshin's remarkable image of IC 2574 on
page 23 clearly shows several bright star-forming regions in
the northeastern end of the galaxy. The brightest of these
stellar nurseries appears as a nebulous knot among a group of
several stars in my 18-inch at 200×. The galaxy is otherwise
uniform in brightness with no central condensation.
Now let's swing back south to the Bear's hind paws. Looking
0.8° west of 3rd-magnitude Mu (μ) Ursae Majoris we
find NGC 3184. I first turned my 18-inch Dob to this lovely
open-faced spiral in December 1999 while seeking the Type II
supernova SN 1999gi, discovered earlier that month. In that
scope, at first glance the 9.8-magnitude galaxy appears large,
round, and of low surface brightness, sporting a rather tiny
core and a 12th-magnitude star on its northern edge. With
longer study, however, two faint spiral arms become detectable.
Revisiting this galaxy with the 30-inch at 300×, the
arms display several branches and a mottled appearance.
Two knots within NGC 3184 have earned their own NGC
designations: NGC 3180 and NGC 3181. The Morphological
Catalogue of Galaxies misidentifies the galaxy as NGC 3180.
NGC 3198 lies 4° north of NGC 3184 and about 2½°
north of 3.5-magnitude Lambda (λ) Ursae Majoris. This
10.3-magnitude, nearly edge-on barred spiral presents a
blotchy, elongated core and a barely discernible nucleus in my
18-inch at 138×. A 12th-magnitude star is perched about 4′
north of the core. William Parsons, the Third Earl of Rosse,
described several " remarkable Nebulae " in a seminal paper
he published in 1850, in which he reported on the " spiral or
curvilinear " features of 14 objects, including NGC 3198. The
nature of nebulae was the subject of significant debate in the
late 19th and early 20th centuries, and Lord Rosse's observations
of M51, the Whirlpool Galaxy, provided the first evidence
of spiral structure - in fact, his 1845 sketch of M51 is iconic.
Below the Bear's Hindquarters
Shifting to targets below the Big Dipper's bowl, we'll start
near Ursa's hind legs with 10.2-magnitude NGC 3675, which
is about 3° east-southeast of 3rd-magnitude Psi (ψ) Ursae
Majoris. In my 18-inch at 197× I note this elongated spiral is
of uneven brightness - the mottled eastern side has a dark
dust lane that sharply cuts off the elongated core. The core is
bright but without a central condensation, and a 13th-magnitude
star resides off the southwestern tip of the galaxy.
GALACTIC WRECKAGE Right next to the glorious pair of M81 and
M82 is NGC 3077, which - with the power of the Hubble Space Telescope
- displays signs of past interactions between its two behemoth
neighbors as in the image above.
Scanning 3.7° north-northeast of NGC 3675 and 2.2°
west-southwest of Chi (χ) Ursae Majoris, we come to NGC
3726. The 10.4-magnitude, nearly open-faced spiral presents
a dappled oval with a small, obvious nucleus, and a 12thmagnitude
star lies off its northern end. In my 30-inch Dob,
I noted the hint of a spiral arm wrapping around the southern
edge of the galaxy toward the east, but that structure isn't
apparent in smaller apertures.
Slewing some 6.4° north-northwest of NGC 3726 we
find NGC 3631. It's about 2° south of the bottom of the Big
Dipper's bowl and nearly equidistant from the bowl stars
Gamma (γ) and Beta (β) Ursae Majoris (Phecda and Merak,
respectively). The 10th-magnitude open-faced spiral is rather
remarkable in larger apertures, displaying at least two arms
outlined by several bright knots. I see only the faintest hint
of its spiral structure in the 10-inch, but it comes alive in
the 18-inch; with the 30-inch, I note that the primary arms
branch into multiple smaller arms.
M108 is 2.8° north-northwest of NGC 3631 - you can
also look for it 1.5° east-southeast of Merak. At magnitude
10.0, it's a bright, elongated cigar-shaped glow with a stellar
nucleus that appears speckled and dusty with several
superimposed stars. I've detected M108 in a 60-mm refractor
at 35×, but it's only just discernible at that aperture.
My 10-inch Dob at 120× reveals an irregular central area
flanked by brighter nodules. Pierre Méchain discovered
M108 and five other objects that were added to the Messier
catalog as M104 through M109 long after Messier's death.
Messier had apparently measured an accurate position for
M108 - along with M109, these entries appear in a handwritten
annotation to Messier's own copy of his catalog, but
he never published them.
sk yand tele scope .o r g * MARCH 2024 21
N
NASA / ESA / J. DALCANTON AND B. WILLIAMS (UNIVERSITY OF WASHINGTON)
http://skyandtelescope.org
Sky & Telescope - March 2024

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