June 2001
Ophiuchus &
Serpens Part 1
Ophiuchus (pronounced
O-fi-kus), although it is one of the larger constellations in the
entire sky, is relatively unknown. Ophiuchus is the Serpernt
Bearer, and the constellations on his left and right are the serpents
(Serpens Cauda (tail) and Serpens Caput (head), representing
the 2 halves of the snake. This month, we focus on the Western half of
Ophiuchus, and Serpens Caput.
Ophiuchus is the "13th Sign" of the Zodiac. The traditional zodiac
signs that you see in the daily newspaper are not astronomically accurate.
The constellations of the zodiac stretch across the entire sky in a narrow
band called the Ecliptic. The ecliptic marks the path that the sun,
moon, and all the major planets take as they travel across the sky. From
late November to mid-December, the sun moves through Ophiuchus. To find
out more about the Signs of the Zodiac, visit our Scorpius
page.
Ophiuchus is easy to find in the early summer sky, around 11:30 p.m. local
time. Tracing its shape is not so easy, but use the bright stars in the
head of Scorpius, low in the southeast, as a guide. The two bright
stars in Libra, (Alpha a, and
Beta b),
point to Serpens Caput, the head of the snake. The "head" of Caput (at
the top right of the above map) is a distinctive pattern of 4 stars in
a wedge shape, very much like the heads of some real serpents. As the night
wears on, bright Altair in Aquila the Eagle rises. Use Altair and
the "wedge" in Caput to find bright Rasalhague (a
Oph), wich lies halfway between
the two. Confusingly, Rasalhague means "head of the snake", when its really
the head of Ophiuchus himself. Tune in next month for Eastern half of Ophiuchus,
plus the mythology behind the Serpent Bearer. Now let's take a look
at the some deep sky objects in Ophiuchus.
This map is adapted from Chris
Dolan's Stars and Constellations page. Ophiuchus is known for its globular
clusters, and in this section we will focus on them. This region contains
some of the finest globulars in the sky. The objects described below are
circled in red on the map. We're going in order of right ascension, with
is left to right on this map. Objects with the binocular symbol in front
will be visible in 7x50 (or similar type) binoculars, while the rest can
only be seen in a telescope.
M5. This globular
in Serpens is absolutely beautiful. At magnitude 5.8 it is visible in all
sizes of scopes. It has a slightly elliptical shape. Just southeast of
M5 lies a gorgeous yellow star (use low power on your telescope to see
them both together). This yellow star is 5 Serpentis, magnitude 5, and
is actually a double star. It's companion is whitish and much dimmer at
magnitude 10.
M107. A dim globular at magnitude 8.1. M107 is in the middle of
an asterism of 3 faint stars that form a low, flattened pyramid.
M12. Another
beauty, M12 at mag. 6.6 should be visible in binocs at a dark sky site.
M12 is very 3-D in a telescope, with a fuzzy unresolved core surrounded
by individual stars.
M10. Nearly
the twin of nearby M12, M10 looks somewhat brighter to the eye, and is
denser with a very bright core.
M62. At this point we delve into Southern Ophiuchus, just east of
the head of Scorpius. M62 is small and fairly faint, possibly because of
its southerly declination. For observers in the Southern Hemisphere, M62
probably looks a lot like M10 and 12.
M19. This globular is part of a trio that lies just west of a diagonal
line of 4 stars, the brightest of which is q,
or Theta Oph. M19 might be a hard target in a 4.5 inch scope, but it is
definitely visible in 6 inch scopes and larger.
NGC 6284. This globular is #2 of the trio, located 1.6 degrees North
of M19. At least a 6 inch scope is needed to see it.
NGC 6293. The third and faintest of the trio, located 1.5 degrees
East of M19. Use low power, and its easy to hop between all three of these
globs.
Check out the Constellation of the Month Archive.
Back to Night Sky Observers main page.