Sky & Telescope - October 2019 - 31

22h 40m

22h 30m
+66°

CASSIOPEIA IM AG E: AKIR A FUJII; CONSTELL ATION
DR AWING: JOH A NNES HE V ELIUS, FIR MAMENTUM
SOBIESCIANUM (1687)

Star magnitudes

M52 has an estimated age of 158 million years, meaning that
we're seeing stars that formed in the Late Jurassic Period,
when Allosaurus, Diplodocus, and Stegosaurus roamed the
American West.
Now we'll take a small step in space, but a giant leap in
time. A bit more than 6° southeast of M52, halfway between
Rho (ρ) and Sigma (σ) Cassiopeiae, you'll find the sprawling
wonder of NGC 7789. The cluster was discovered by Caroline
Herschel in 1783, and it's also known as "Caroline's Rose" for
its concentrically-curving loops and chains of stars. This is
no bloom of youth, however - NGC 7789 is 1.7 billion years
old, dating to a time when microbial mats were cranking out
Earth's early oxygen atmosphere.
h
m
We'll follow the zig from M52
23h 50m 23h 40m 23h 30m 23h 20m 23h 10m 23h 00m 22 50
to NGC 7789 with a zag 5.5° to the
f
northeast, to the bright cluster NGC
4
CEPHEUS
129. My early observing notes read,
5
"compact, many stars, probably better
6
than M103 under dark skies." Indeed,
The King's
7
one of the enduring mysteries of CasGift
8
siopeia is how Charles Messier and his
9
assistant, Pierre Méchain, managed to
find nice but unexceptional clusters
like M52 and M103 while overlooking so many brighter showpieces.
NGC 129 was discovered by William
CASSIOPEIA
Herschel in 1788, just five years after
his sister discovered her eponymous
rose. See if you can tease out a perfect
4
triangle of 9th-magnitude stars at the
center of the cluster.
M52
We'll now drop a few degrees south
to visit Schedar, or Alpha Cassiopeiae. Schedar is Arabic for "chest," and
this queen's heart holds a secret: an
8th-magnitude companion 69″ to the
Cassiopeia
west. The two form an optical double,
only coincidentally aligned as seen
from Earth, rather than a true binary.
Schedar itself is a K-class orange giant.
ε
At 4-5 times the mass of the Sun, the
star is destined to blow off its outer lay129
γ
ers and form a planetary nebula before
654
going into a long retirement as a white
663
Stock 2
dwarf.
659
M103
δ
Our next stop is a perennial favorite
for binocular and telescopic observers
η
457
alike: NGC 457, the Owl or ET Cluster.
u W IS FOR OPEN CLUSTER About 106 of
the galaxy's 1,100 open clusters lie within the
bounds of Cassiopeia. The familiar W asterism
(or M, if you prefer) of Cassiopeia makes a
good starting point, as several clusters, including M103, NGC 663, NGC 654, and NGC 659,
sparkle near her legs.

+64°
30

+62°

7790

β
ρ
7789
σ

α

884
869

sk yandtele scope.com * OCTOBE R 2 019

31



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Sky & Telescope - October 2019

Table of Contents for the Digital Edition of Sky & Telescope - October 2019

Contents
Sky & Telescope - October 2019 - Cover1
Sky & Telescope - October 2019 - Cover2
Sky & Telescope - October 2019 - 1
Sky & Telescope - October 2019 - Contents
Sky & Telescope - October 2019 - 3
Sky & Telescope - October 2019 - 4
Sky & Telescope - October 2019 - 5
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