The group of stars has been known by the name Ophiuchus for two thousand years
or more. What is not known, though, is why the name 'Serpent Holder' was assigned to them.
Some suggest that the constellation represents Asclepius or Aesculapius, the
healer of Greek myth whose cult was closely associated with serpents. This identification
is by no means certain.
More famous than any of these is Barnard's Star, which lies just under six light years
from Earth, and is one of the Sun's closest neighbours. It is a very small and faint
redstar of the type known as subdwarfs, so that despite being so nearby, it is invisible
to the naked eye.
When the zodiac was first delineated by the ancients, it consisted of twelve 'houses',
each associated with one of twelve constellations that lay along the Ecliptic: Aries,
Taurus, Gemini, Cancer, and so on. Since that time, gravitational effects on the
orbit of the Earth, known as 'precession', have caused the line of the Ecliptic to change slightly.
Specifically, it now passes through thirteenconstellations, with Ophiuchus
being the new addition. Where the Sun once passed directly from Scorpius into
Sagittarius, it now spends nineteen days each year, from 30 November to 18 December, in the
new 'house' of the Serpent Holder.