PUBLIC DOMAIN / WIKIMEDIA COMMONS
I
t seems to me that Ophiuchus often
gets a low rating from beginners for its
supposed lack of observational thrills.
It’s true that the star pattern of the Ser-
pent Bearer is big but rangy, with a large
center that has no bright stars. And
though the constellation’s globular clus-
ters are amazingly numerous, they’re
smaller and dimmer than the mighty
globular blazes in neighboring Serpens,
Hercules, Scorpius, and Sagittarius.
Perhaps it’s true that Ophiuchus
doesn’t offer the brightest splashy
wonders for small telescopes and novice
observers, but the incredible variety
of its attractions can help improve a
beginner’s observing skills and lead to
a greater awareness of the diversity of
deep-sky objects in the heavens.
Diversity? Next month we’ll explore
the constellation’s collection of globu-
lars, its two huge open clusters, its
many fi ne double and multiple stars, its
surprisingly prominent dark nebulae,
and its pair of superb planetary nebu-
lae. We’ll also meet the second-closest
star in the night sky.
But this month, let’s meet Ophiuchus
in the context of its remarkable connec-
tions to its constellation neighbors.
Ophiuchus and Serpens. Ophiu-
chus is a large, human fi gure pictured
holding a snake: Serpens the Serpent.
Of the 88 offi cial constellations, Ser-
pens is the only one separated into two
parts by another constellation. To the
west of Ophiuchus is the front part of
the snake, known as Serpens Caput (the
Serpent’s Head), and to its east is Ser-
pens Cauda (the Serpent’s Tail). Com-
bined, Ophiuchus and Serpens stretch
all the way from Boötes to Aquila,
with Ophiuchus’s brightest star, 2nd-
magnitude Rasalhague, slightly below a
long, long line connecting Arcturus and
Altair. If we counted the areas occupied
by Ophiuchus and Serpens together asOphiuchus and Friends
The celestial serpent bearer has plenty of interesting company.
a single constellation, it would be by far
the largest in the heavens.
This arrangement of Ophiuchus
dividing Serpens in two is not just
unique, it’s visual ly striking. The
interesting lights that go before and
after Ophiuchus are Unukalhai (Alpha
Serpentis) in Serpens Caput, and Alya
(Theta Serpentis) in Serpens Cauda.
Unukalhai is a magnitude-2.6 orange
star and is a rough guide to the vicinity
of M5, one of the grand globular clusters
and a favorite of many observers. The
5.8-magnitude cluster is situated about
8 ° southwest of Unukalhai and just 20 ′
northwest of the golden, 5.1-magni-
tude star 5 Serpentis. And what about
Alya? It’s a beautiful, easy double star
comprised of magnitude-4.6 and -4.9
components (both white, A5-type stars)
a generous 22 .3′′ apart. Alya is also the
very end of the Serpent’s tail — a line ofstars jutting into the dark Great Rift of
the summer Milky Way.
Ophiuchus and Hercules. The
Alpha stars of Ophiuchus and Her-
cules are Rasalhague and Rasalgethi,
respectively. They’re only 6° apart and
mark the heads of the two big fi gures.
Hercules is the most famous legendary
strongman, while Ophiuchus is usually
associated with Aesculapius, the god
of medicine, whose snake-entwined
staff remains a symbol of the medi-
cal profession today. Which constel-
lation is bigger? The main pattern of
Ophiuchus appears much larger, but
Hercules includes an expansive region
of dim naked-eye stars and occupies a
signifi cantly greater area. Even though
Ophiuchus is the 11th-biggest constella-
tion, Hercules ranks 5th.
Ophiuchus and Scorpius. The
modern boundaries of the constella-
tions have the Sun spending only one
week in Scorpius but almost three weeks
in Ophiuchus. Because of this, some
have started calling Ophiuchus the 13th
constellation of the zodiac.¢FRED SCHAAF welcomes your letters
and comments at [email protected].Under the Stars by Fred Schaafskyandtelescope.org • JUNE 2020 45
pSERPENT TAMER This fanciful chart from Alexander Jamieson’s 1822 Celestial Atlas portrays
the constellations Ophiuchus and Serpens.