62 ASTRONOMY • DECEMBER 2019
BINOCULAR UNIVERSE
As the Sun sets in December, we find Cassiopeia
the Queen near the zenith, as if reigning over
all of her loyal stellar subjects. The constella-
tion’s eye-catching W shape makes Cassiopeia one of the
first constellations that most new stargazers learn.
The gentle glow of our galaxy f lows past those five
stars, bringing with it many binocular treasures. You’ll
need to crane your neck to enjoy them, however, so take
a moment to set up a chaise lounge. Then lie back and
raise your binoculars high.
This month, let’s first turn our attention
toward the western portion of Cassiopeia. By
connecting a line from Schedar (Alpha [α]
Cassiopeiae) to Caph (Beta [β] Cas) and then
extending it an equal distance beyond, you’ll
arrive at the open cluster M 52. Discovered
on September 7, 1774, by Charles Messier
himself, M 52 is an easy catch through just
about any binocular. An estimated 200 stars
call the cluster home, though only a few are
bright enough to be seen in binoculars. The
rest blend into a fog of stardust.
Just beyond M52 is a slender diamond of four 5th- and
6th-magnitude stars, along with an arc of four fainter stars
curving farther northwest. To the late Massachusetts
amateur astronomer John Davis, these stars appeared to
form an airplane. As he once explained it to me, “The
plane’s brightest star (red giant 4 Cassiopeiae) marks a light
at the end of the eastern wing, while a lone 6th-magnitude
star lies at the tip of the western wing. A short arc of faint
stars stretching northward forms the plane’s crooked tail.”
The diamond-shaped wingspan of Davis’ Airplane
extends 1° tip to tip, as does the curved fuselage.Scan back toward Caph and then hook southwest to
4.5-magnitude Rho (ρ) Cassiopeiae. If you recall in last
month’s column, we visited Mu (μ) Cephei, which is one
of the largest stars visible through binoculars. Well, Rho
Cas may not be quite as large, but it’s still between 400
and 500 times the diameter of our Sun. If we replaced our
Sun with Rho, the outer edge of its photosphere would
engulf the four inner planets and extend into the asteroid
belt. Rho is classified as a yellow hypergiant, an extremely
rare type of star. Yellow hypergiants are among the most
luminous stars, and only 15 are known in the Milky Way.
In his book, Observing the Night Sky with Binoculars
(Cambridge University Press, 2008), fellow columnist
Stephen James O’Meara describes Rho as a “delicious
pumpkin color,” a most appropriate description as the
season of pumpkin spice everything draws to a close.
A s you ad m i re R ho, you’ l l probably not ic e a rou nd g low
less than a degree south-southeast. That is NGC 7789, a
rich open cluster of over 500 stars lying 8,000 light-years
away. NGC 7789 is often referred to as Caroline’s Rose
after Caroline Herschel, who discovered this copious
cluster in 1783. None of its stars is brighter than 11th
magnitude, unfortunately, which is below the threshold
of most binoculars. Instead, we see their collective glow
spanning about the same apparent diameter as the Full
Moon. If your binoculars are 70mm or larger, however,
there’s hope of spotting a few of those dim denizens peek-
ing out from the haze. How many can you count?
Our last stop this month is a fun asterism invented by
British amateur astronomer Eddie Carpenter. Known as
Eddie’s Coaster, this meandering, double-dipping wave
of faint stars lies about 3° north-northeast of
Gamma (γ) Cassiopeiae, at the center of
the W. Eddie’s Coaster includes more than a
dozen stars spanning 2.7°. The chance align-
ment reminded Carpenter of an amusement
park roller coaster, which led to the asterism’s
name. Admittedly, as we face north this
month, the coaster will appear upside down,
but use your imagination. If we ride the
coaster from west to east, it starts at 7th-
magnitude HD 4841 and then slowly
ascends. After topping out, it drops to 8th-
magnitude HD 5915, only to rise again before a second,
steeper drop brings our ride to an end at 7th-magnitude
HD 7156. All together, they stand out nicely through my
10x50 binoculars from my suburban yard.
Have you ever found an asterism that you’d like to
share with the rest of us? Contact me through my website,
http://www.philharrington.net, and tell me about it.
Until next month, remember that two eyes are better
than one.Cassiopeia offers multiple dazzling binocular targets.
The Queen’s court
The bright open
cluster M52 in
Cassiopeia offers a
splash of stars for
any observer armed
with binoculars.
ANTHONY AYIOMAMITISCassiopeia is
one of the first
constellations
that most new
stargazers
learn.
BY PHIL
HARRINGTON
Phil is a longtime
contributor to
Astronomy and the
author of many books.BROWSE THE “BINOCULAR UNIVERSE” ARCHIVE AT
http://www.Astronomy.com/Harrington