My first Magazine Sky & Telescope - 01.2019 | Page 45

M36
AURIGA
θ
M37
χ
26
Galactic +
anticenter
κ
5°
bin
β
Elnath
ocular vie w
GEMINI
M35
Cr 89
TAURUS
M1
η
µ
Binocular Highlight by Mathew Wedel
The Galactic Rim
I
WHEN TO
USE THE MAP
Late Nov
Early Dec
Late Dec
Early Jan
Late Jan
11 p.m.
10 p.m.
9 p.m.
8 p.m.
Dusk
These are standard times.
n the summer, we look galactically inward, toward
the inner arms and core of the Milky Way. Like
someone lying down in a meadow and gazing at
nearby mountains, we see i rst the closest stars and
clusters (the grass), then the more distant stars, clus-
ters, and nebulae that dei ne the inner spiral arms
(the trees), and i nally the galaxy’s vast central bulge
looming in the distance (the mountains).
In the winter Milky Way, we look in the opposite
direction, outward toward the edge of the galaxy. The
galaxy has only one center, but for every observer it
also has an anticenter, the point 180° around the sky
from the galactic core. For us, that point lies in the
constellation Auriga, the Charioteer. No bright star
marks this galactic antipode, but it’s easy to i nd.
Imagine a fl attened diamond, 7° across, with three
corners marked by the open cluster M37 and the
stars Chi (χ) Aurigae and Beta (β) Tauri (Elnath). The
invisible fourth corner, opposite Chi Aurigae, is the
position of the galactic anticenter.
Almost all of the visible stars in this direction, and
many of the open clusters, belong to our own Orion
Spur — they’re grass, or maybe shrubs. The forest
beyond is the Perseus Arm, the backbone of which
lies a little more than 6,000 light-years away. As a
rough rule of thumb, objects closer than 3,000 light-
years are our neighbors in the Orion Spur, including
the clusters M35 and Collinder 89 in Gemini, and
virtually all the clusters in Taurus, the Bull. In contrast,
objects that lie 4,000 or more light-years away belong
to the Perseus Arm, which encompasses the Messier
trio of M37, M36, and M38 in Auriga, and M1 in
Taurus. This is as simple as the Milky Way gets — and
it’s still a lot to take in.
¢ MATT WEDEL is exploring “down under,” galac-
tically speaking. G’day, mates — or rather, g’night!
sk yandtele scope.com • JA N UA RY 2 019
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