Sky & Telescope - February 2023 - 20

Targets for an Audience
as its mythological
twin Pollux. The
two component
stars of the visual
pair are about
twice as far apart
as the Sun and
Pluto, with a mean
separation of 104
astronomical units.
And they take 460
years to orbit each
other. You might
also want to tell
them that Castor
is actually a system
of six stars in three
binary pairs - each
member of the
visual pair is itself
a spectroscopic
binary. A third
spectroscopic pair
consisting of two
red dwarfs sitting
72″ to the south
appears to be gravitationally
bound
to the other two
pairs. If you relate
facts like these, be
TANTALIZING TARGETS FOR
WINTER AUDIENCES A fun
variety of celestial objects
populates the winter sky with
which to regale guests at your
outreach events. Use your
laser pointer (if you have one)
to outline the constellations.
Note that the stars of Puppis
are outside the bottom end of
the frame.
Castor
GEM I N I
κ
NGC 2392
λ
TAURU S
CA N I S M I NOR
NGC 2264
MONOCEROS
NGC 2024
B33
IC 434
M42
M46
PU PPI S
CANI S MAJOR
prepared to explain terminology like " astronomical unit " or
" spectroscopic. " Even terms like " binary " may be unfamiliar
to your audience.
Having answers at your fingertips to your guests' queries
will bolster your confidence and enhance your audience's
experience. Heed the sage words of Abraham Lincoln: " Give
me six hours to chop down a tree, and I will spend the first
four sharpening the axe. "
Captivating Clusters
Bright open clusters are usually a good choice for outreach
targets. They're pretty and can be very impressive. I like to
show clusters that have curious and recognizable patterns
that make observing them fun and surprising.
One winter favorite is NGC 457 in Cassiopeia. It's alternately
known as the Owl Cluster, the E. T. Cluster, or the
Dragonfly Cluster. Two bright stars give the impression of eyes
and a scattered pattern of fainter stars represent a body with
wings or arms spread wide. Asking an audience to use their
imagination to see one of these suggested shapes is a good
way to spark engagement and introduce a bit of whimsy.
This young star cluster contains about 100 stars, spans 53
light-years in diameter, and is around 9,100 light-years away.
William Herschel discovered it in 1787. The 5.0-magnitude
20 FEBRUARY 2023 * SKY & TELESCOPE
ORION
ξ
ν
NGC 2169
AURIGA
Pleiades
CAS S I O P EIA
NGC 457
ε
Double Cluster
δ
P ERSEU S
yellow supergiant
Phi (φ) Cassiopeiae
and 7.0-magnitude
HD 7902 form
the two eyes, but
Phi Cassiopeiae
is unlikely to be
a cluster member.
Most novice
observers may not
spy the fine red star
V466 Cassiopeiae
on the cluster's
northern edge
unless you point
it out but will be
impressed when
they do spot it.
Imagining a line
connecting Epsilon
(ε) and Delta (δ)
Cassiopeiae and
extending it about
another third of the
distance between
them will lead
you to NGC 457.
I often employ a
green laser pointer
during my outreach
sessions - they're
useful tools that will usually grab the attention of a crowd. In
fact, you might find some in your audience more impressed by
the laser than by the view in the telescope! Once the novelty
wears off, however, a laser is a great way to point out your
target and guide your guests to it in the sky. Sometimes it's all
you need to conduct a successful outreach event, as they're
perfect for tracing out the constellations and identifying the
named stars. Lasers can be dangerous, so a word of caution is
in order here (see sidebar at right).
NGC 2169 in Orion is another example of an open
cluster whose stars form an interesting asterism. This small
group contains about 30 stars, and the brightest of them are
arranged like the number 37 when viewed in a non-inverting
scope. Many astronomers actually call it the 37 Cluster, and
it's sure to amuse first-time viewers. Located a short hop from
Betelgeuse in Orion's raised arm, it forms the apex of a triangle
with Xi (ξ) and Nu (ν) Orionis at its base. The cluster is
about ½° southwest of a line connecting the two stars.
Recognizable patterns add considerable interest to objects
and encourage viewers to examine them more closely. At first,
you may have to help the observer see a Christmas tree in
NGC 2264, but once they recognize it, they'll have a sense
of accomplishment. I like to describe it as a Christmas tree
cookie, as the asterism resembles that shape very well. If the
AKIRA FUJII
Sky & Telescope - February 2023

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