In 1999-2001 the location of the winter solstice will
move into exact conjunction with the galactic equator.
It will not return to this position for 25,920 years!
(1999-2001 can be seen as the moment of "totality"
of a "galactic eclipse" that lasts from 1983-2019--
see note at the end of the page.)
December 22, 1980
The horizontal red line on which the sun is located here is
the ecliptic (also known as the zodiac), and does not move.
The purple line is the galactic equator (the equator of our Milky
Way spiral galaxy), which also does not move. The vertical red
line is the solsticial colure, which *is* slowly moving because of
the "precession of the equinoxes" (the very gradual wobble
of the earth's axis that is also responsible for the famous shift-- sometime
in the next few hundred years-- of the spring equinox into Aquarius). As
the solsticial colure moves, so does the point where it intersects with the
ecliptic: this intersection point is the location of the winter solstice
(the place on the ecliptic where the sun is at the beginning of winter).
The image above is a picture of the sky on December 22, 1980 and here the
winter solstice (the point where the two red lines cross) is a bit to the
the intersection point of the galactic equator and the ecliptic (the point
where the purple line crosses the horizontal red line).
December 22, 1999
Here the winter solstice has moved to the right, and is located
exactly at the intersection of the galactic equator with the ecliptic!
This conjunction will be more or less exact from 1999
December 22, 2020
Here the winter solstice has moved on, and is now to
the right of the intersection of the galactic equator and
the ecliptic. It will not return to this point for 25,920 years,
although 12,960 years from now it will reach the other point
where the galactic equator intersects the ecliptic, exactly
opposite this one.
Note: the above diagrams are all calculated for December 22,
the day *after* the solstice. This is because on the solstice
itself the sun would cover the area of the sky where the
intersection of the ecliptic and the galactic equator is located,
making it impossible to see in the diagram. In other words, on
the solstice itself in 1999-2001 the sun will exactly "occult"
(cross in front of) the intersection of the ecliptic and the galactic
equator. Interestingly, because the sun is 1/2 degree in width,
and the solstice takes 72 years to move one degree, the
sun will actually occult the ecliptic/galactic intersection on the solstice
for 36 years (1999-2001 is the mid-point of this period of occultation,
when the exact center of the solar disc lies on the galactic equator at
the moment of the solstice). So this solar passage over the galactic
equator-- what we could call a "galactic eclipse"-- actually began
1983 and will continue until 2019, with "totality" occuring now!
(Note: images were made using "REDSHIFT 3"