Conjunction (astronomy and astrology)
Conjunction is a term used in positional as-
tronomy and astrology. It means that, as seen
from some place (usually the Earth), two ce-
lestial bodies appear near one another in the
sky. The event is also sometimes known as an
appulse.
The astronomical and astrological symbol
of conjunction is ?(in Unicode x260c) and
handwritten:
Three consecutive days of close conjunction
between the Moon and Venus.
Passing close
More generally, in the particular case of two
planets, it means that they merely have the
same right ascension (and hence the same
hour angle). This is called conjunction in
right ascension. However, there is also the
term conjunction in ecliptical longitude. At
such conjunction both objects have the same
ecliptical longitude. Conjunction in right as-
cension and conjunction in ecliptical longit-
ude do not normally take place at the same
time, but in most cases nearly at the same
time. However, at triple conjunctions, it is
possible that a conjunction only in right as-
cension (or ecliptical length) occur. At the
time of conjunction - it does not matter if in
right ascension or in ecliptical longitude - the
involved planets are close together upon the
celestial sphere. In the vast majority of such
cases, one of the planets will appear to pass
north or south of the other.
Passing closer
However, if two celestial bodies attain the
same declination at the time of a conjunction
in right ascension (or the same ecliptical lat-
itude at a conjunction in ecliptical longitude),
the one that is closer to the Earth will pass in
front of the other. In such a case, a syzygy
takes place. If one object moves into the
shadow of another, the event is an eclipse.
For example, if the Moon passes into the
shadow of Earth and disappears from view,
this event is called a lunar eclipse. If the vis-
ible disk of the nearer object is considerably
smaller than that of the farther object, the
event is called a transit. When Mercury
passes in front of the Sun, it is a transit of
Mercury, and