Sky and Telescope - March 2017 - 58

MARCH 2017 OBSERVING
Going Deep

u NGC 4157 straddles the border between
Ursa Major and Canes Venatici. Look for a
thickened needle of light running east-northeast to west-southwest. The image at right
was captured with the 32-inch Schulman
Ritchey-Chrétien telescope at the Mt. Lemmon SkyCenter.
q Taken with a 20-inch Ritchey-Chrétien
telescope as part of the Kitt Peak Advanced
Observing Program, the image below reveals
the spiral structure of NGC 4100. The galaxy
will show as an elongated smudge with a
faintly brighter core in the eyepiece.

NGC 4100

M A R C H 2 0 1 7 * SK Y & TELESCOPE

9, 2015. At 152× the 16-inch reﬂector
showed a bright, spindle-shaped galaxy
elongated 6:1 [Gottlieb 5:2] and lying
northeast to southwest. The very gradually brighter round core holds a nucleus.
The mottled galaxy has a knot near the
northeastern tip of the halo. A second
look showed elongated knots towards
both tips of the halo, more prominently
at the northeastern end. "These must
be spiral arms," I thought. After upping
the power to 203× it clearly looked like a
northeastern spiral arm looping around
and ending at a knot on the arm just
northwest of the nucleus. I also detected
what I thought was a tiny knot near
the northeastern tip of the galaxy, but
was actually the brightest part of the
detached arm segment that earned NGC
4088 its place as No. 18 in Arp's Atlas of
Peculiar Galaxies. But 203× didn't show

NGC 4157

NGC 410 0: JACK BURG ESS / A DA M BLOCK / NOAO / AUR A / NSF; NGC 4157: JOSEPH D. SCHULM A N / CC BY-SA 3.0

Westernmost NGC 4026, a northsouth lenticular galaxy, contains a
super-massive black hole. In my 16-inch
at 229× a brilliant nucleus dominates
this edge-on. The extremely thin disk is
a very faint needle, elongated perhaps
15:1 [Gottlieb 5:1].
Southernmost NGC 4100 appears as
an open-armed barred spiral in photographs. At 229× in the 16-inch it runs
north-northwest to south-southeast,
and is elongated 8:1 [Gottlieb 3:1]. It
shows a faint nucleus, with a knot at
the southern end of the disk.
NGC 4157, on the border with Canes
Venatici, is a spiral galaxy of type SABb.
In the 16-inch at 229× it appears about
5′ long, a 12:1 [Gottlieb 7:1] splinter in

position angle 66° (east-northeast to
west-southwest) with a very elongated
core. The fairly faint nucleus was only
intermittently visible. I found knots at
both the preceding and following ends of
the disk - they, too, were only intermittently visible. The preceding end of the
core seemed to be crossed by a transverse
dark lane. This galaxy is a winner!
A sketch made by Atlanta observer
and Sky & Telescope contributor Richard
Jakiel with a 20-inch f/4.5 at 175× shows
a long dust lane along the northwestern
side of NGC 4157's disk, but I couldn't
detect it with my smaller scope.
Large NGC 4088, an SABbc galaxy,
was one of the "spiral nebulae" whose
arms were discovered visually with Lord
Rosse's 72-inch Leviathan at Birr Castle
in Ireland. After a decade of trying,
I ﬁnally saw spiral structure on June

Sky and Telescope - March 2017

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