constellation corner
Cassiopeia offers bounty of star clusters
COURTESY OF Mike Wiles
Astrophotographer Mike Wiles used an Explore Scientific ED152 f/8 refractor telescope and a SBIG ST-
8300M camera to capture these stunning images of the White Rose Cluster, above, and Messier 52, below.
COURTESY OF Mike Wiles
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In mythology, Cassiopeia
was a vain creature undone
by her arrogance. But the
circumpolar constellation that
bears her name certainly has
some celestial beauties worth
boasting about.
Visible from 90° north to 20°
south, Cassiopeia is known
for the striking “W”-shaped
asterism that is formed by
its five brightest stars. The
yellow-white giant Beta
Cassiopeiae anchors one end
of the “W.” Also known as
Caph, this star is one of the
brightest Delta Scuti type
variables to grace the sky
and has an average apparent
magnitude of 2.27. The
next point in the “W” is the
orange giant Schedar (Alpha
Cassiopeiae), which marks the
heart of the doomed queen.
The brilliant blue Gamma
Cassiopeiae lies at the center
of the famous asterism.
Categorized as an eruptive
variable, this star can outshine
both Schedar and Caph when
its intensity peaks. Nicknamed
Navi by U.S. Astronaut
Gus Grissom because of its
usefulness as a navigational
point in space, Gamma
Cassiopeiae has a bulging
equator due to rapid rotation
and is also a spectroscopic
binary.
The next point in the “W”
is Delta Cassiopeiae, which
is an eclipsing binary that is
also identified as Ruchbah.
Its apparent magnitude varies
between 2.68 and 2.74.
The last star that defines
the asterism is Epsilon
Cassiopeiae, which is also
Sky ’ s
Up
known as Segin. Located
about 440 light years
away, this blue-white giant
shines from its post with an
apparent magnitude of 3.38.
The queen’s notable stellar
offerings continue beyond
the five that define her most
recognizable feature. Best
viewed with a telescope, Eta
Cassiopeiae is a beautiful
binary star system with
a yellow dwarf primary
component that is much
like our own star and an
orange dwarf companion.
Cassiopeia is also home to
two stars in the very rare
yellow hypergiant class -
Rho Cassiopeiae and V509
Cassiopeiae. Although they
are each located thousands
COURTESY OF John O’Neill
The Bubble Nebula is a diffuse nebula located southwest of Messier 52. Astrophotographer John O’Neill
of light years from Earth,
captured this image using an Explore Scientific ED127-FCD100 and an SBIG ST-10 XME camera through narrow
their extreme luminosity
band filters of Ha, Oiii and Sii. Exposure times were three 800 second subs through each filter.
keeps them visible to the
naked eye.
A quick tour of Cassiopeia’s deep
sky offerings has to begin with the
open cluster Messier 52. Although
it can be enjoyed with binoculars, a
moderate-sized telescope will reveal
it as a fan of faint stars that includes
a couple of bright yellow giants – one
of which pops out from the cluster’s
southwestern edge. A far more remote
open cluster is Messier 103, which is
best viewed through binoculars due
to its loose structure. Located near
Ruchbah, the cluster, which includes
a red giant that truly shines in
photographs, will manifest as a hazy
V-shaped patch.
Another treat is the “The White Rose
Cluster,” which is also known as
“Caroline’s Rose Cluster” because it
was discovered by famed astronomer
COURTESY OF Mike Wiles
Caroline Herschel. The cluster’s
Astrophotographer Mike Wiles used an Explore Scientific ED152 f/8 refractor telescope and a SBIG
pattern of bright stars and dark paths
is similar to the curves and valleys of ST-8300M camera to capture this image of Messier 103.
around 100 stars and is sometimes
galaxy in our local group; and the
a blooming rose.
called the Owl Cluster or ET Cluster
Pacman Nebula, an emission nebula
The constellation also offers the
due to an eye-like pairing of two
with an open cluster of brilliant blue
Bubble Nebula, which is a diffuse
bright stars; the irregular galaxy
supergiants at its core and several
nebula southwest of M52; the open
IC 10, which is the only starburst
Bok globules.
star cluster NGC 457, which has
Sky ’ s
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