Astronomy - USA (2020-04)

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Through a 10-inch tele-
scope, observe NGC 4731’s
long, relatively bright central
bar. If your observing site is
dark, crank up the power past
200x and look at the wide,
irregular spiral arms that orig-
inate from each side of the bar.
The western arm appears
somewhat brighter. Tiny
bright patches within both
arms signal hotspots of star
formation. Through a 20-inch
or larger telescope, use a neb-
ula filter to increase the con-
trast of those regions and the
galaxy’s older stars.
If you want to show some-
one an edge-on galaxy, the
next object on our list will do
nicely. Barred spiral NGC
4762 glows at magnitude
10.3. More than four times as
long as it is wide (9.1' by 2.2'),
NGC 4762 appears as a white
line through medium-sized
telescopes.
You won’t see a central
bulge through any size scope.
All you will notice is that the
core appears ever-so-slightly
brighter than the arms.
Next up is NGC 4856, a
magnitude 10.4 spiral that lies
near Virgo’s western border
with Corvus. Through an
8-inch telescope at 200x,

you’ll see a disk with a small,

bright central region. The gal-

axy stretches more than three

times as long as it is wide (4.3'

by 1.2') in a northeast-to-

southwest orientation. For

those of you using 14-inch or

larger scopes, crank the power

past 350x and look for a mag-

nitude 13.1 foreground star

just barely east of the core.

At magnitude 13.9, you

might be inclined to skip the

next target, planetary nebula

IC 972, for less difficult fare.

That’s fine if you’re viewing

through a 4-inch scope, but if

you have a 10-inch or larger

instrument, have a look at the

faint outer layers of this once

Sun-like star. Because of its

small size (43"), IC 972 has a

reasonable surface brightness.

Better known as Abell 37, this

object appears uniformly illu-

minated with a sharp edge.

Our final target is globu-

lar cluster NGC 5634. If

we’re being honest, Virgo is

known for its galaxies. The

constellation contains some

200 deep-sky objects brighter

than 13th magnitude. Only

one — magnitude 9.5 NGC

5634 — is a globular cluster.

Point a 4-inch telescope at

it, and you’ll see lots of faint

stars and one bright orange

one — magnitude 8.0 SAO

139967, which sits a bit more

than 1' east-southeast of the

cluster’s center. The star isn’t

part of NGC 5634, it just hap-

pens to lie in the same direc-

tion from our viewpoint.

The cluster’s stars are con-

densed, meaning you won’t

easily resolve them into indi-

vidual points. But the back-

and-forth visibility battle

you’ll encounter between the

star and the cluster makes for

a fascinating observation.

As you’ve probably

inferred, there are a great

many more targets in Virgo.

The ones on this list, how-

ever, should keep your scope

pointed in this constellation’s

direction for a full night.

Take your time, sit comfort-

ably as you observe, and

enjoy the view.

GAMMA

VIRGINIS HAS

BEEN THE

SUBJECT

OF MUCH

RESEARCH, AND

ASTRONOMERS

HAVE EVEN

WRITTEN POEMS

ABOUT IT.

ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

PAUL AND DANIEL KOBLAS/ADAM BLOCK/NOAO/AURA/NSF

Michael E. Bakich is a contributing

editor of Astronomy who loves to spend

a night viewing objects in a single

constellation.

M90

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