Australian Sky & Telescope — July 2017

42 AUSTRALIAN SKY & TELESCOPE July 2017

The serpent’s fang

L

ike a lot of stargazers, I often go observing to escape the hassles

of life. Serpens Caput, the head of the celestial snake, is a

pretty good getaway spot, with a variety of things to see and

do. I like to start with the wide, not-quite-a-triangle formed by Beta

(β), Gamma (γ), Iota (ι) and Kappa (κ) Serpentis. Most atlases use

this group as the ‘head’ of the constellation. That artistic decision

is fitting, because the various stars of Tau (τ) Serpentis form a

fang-shaped asterism 5° long that points west. The chains of stars,

culminating in bright Tau1 Serpentis, even curve like a fang.

If the Tau stars form the serpent’s fang, the group of bright stars

running southwest from Gamma to Delta (δ) Serpentis can be seen

as the curving hood of a cobra as it rears back to strike. The stars

of the fang and the hood are not physically related, though. In both

cases, they’re a mix of nearby main-sequence stars with a handful of

more distant giants, scattered over several hundred light-years along

our line of sight. But they are fun to trace out with binoculars.

If you like binocular double stars, this is a rich area. Tau^2 and

Tau^4 Serpentis are wide optical doubles that seem to mirror each

other across an imaginary line extending southwest from Tau^5

Serpentis. Beta Serpentis is another optical double, tighter but still

easily split in low-power binoculars. And pop over the border into

Hercules to check out the pairing of Kappa and 8 Herculis. Kappa is

itself a close (27′′) pair of orange giants, which contrast nicely with

8 Herculis, a white A-class main-sequence star.

■MATT WEDEL likes to kick back with his binoculars on his driveway.

5

8

κ

φ

τ^2 τ

1

δ

τ^3

τ^7

τ^8

τ^4

τ^5

τ^6

χ

ι

β

υ

κ

ρ

γ

SERPENS

CAPUT

Serpent’s

Fang

5 °^ binocular (^) v
iew
21
h
SAGITTA
AQUILA
CAPRICORNUS
PISCIS AUSTRIN
M30
57
Altair
α
γ
ζ
β
α
η
θ
Fa
ci
n
aF
c
in
g
Ea
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gn
EN
WHEN
EarlyJune 10p.m.
Late June 9 p.m.
Early July 8 p.m.
Late July 7 p.m.
These are standard times.
HOW
Go outside within an hour or
so of a time listed above. Hold
the map out in front of you
and turn it around so the label
for the direction you’re facing
(such as west or northeast) is
right-side up. The curved edge
represents the horizon, and the
stars above it on the map now
match the stars in front of you
in the sky. The centre of the
map is the zenith, the point in
the sky directly overhead.
FOR EXAMPLE: Turn the
map so the label ‘Facing North’
is right-side up. About halfway
from there to the map’s centre
is the bright star Arcturus. Go
out and look north nearly half-
way from horizontal to straight
up. There’s Arcturus!
NOTE: The map is plot-
ted for 35° south latitude (for
example, Sydney, Buenos
Aires, Cape Town). If you’re
far north of there, stars in the
northern part of the sky will be
higher and stars in the south
lower. Far south of 35° the
reverse is true.
ONLINE
You can get a real-time sky chart
for your location at
skychart.skyandtelescope.com/
skychart.php
USING THE
STAR CHART
–1
Star
magnitudes
0
1
2
3
4
BINOCULAR HIGHLIGHT by Matt Wedel
57
ζ
δ
in
g
gn