CELESTIALSPHERE
The celestial sphere can be understood by imag-
ining that all the objects in the sky are stuck
against the inside of a gigantic hollow sphere,
with Earth located at the exact center. The
basic notion of the celestial sphere is assumed in
various systems for locating celestial bodies in
terms of celestial coordinates. Very much like
terrestrial coordinates, which involve specifying
a location in terms of longitude and latitude,
celestial coordinates require two measurements
of distance, expressed in terms of degrees of a
circle. The altitude-azimuth systembegins by situ-
ating itself at a specific location on the Earth’s
surface, and uses the horizon, the zenith, and
the north-south axis as points of reference. The
equatorial system uses the celestial equator
(Earth’s equator extended out into space and
projected against the backdrop of the celestial
sphere) and the vernal point (where the Sun is
located at the point of the spring equinox) as its
points of reference. Astronomers most often use
the equatorial system. The ecliptic systemuses
the ecliptic (the orbit of Earth around the Sun,
projected outward against the celestial sphere)
and the vernal point. Astrologers use the eclip-
tic system.
Sources:
Brau, Jean-Louis, Helen Weaver, and Allan Edmands.
Larousse Encyclopedia of Astrology.New York: New American Library, 1980.
Filbey, John, and Peter Filbey. The Astrologer’s Companion.Wellingborough, Northamptonshire,
UK: Aquarian Press, 1986.
CENTAURS
Centaurs by definition originate in the Kuiper Belt, whose orbits come inside the
outer planets. More specifically, a Centaur possesses a perihelion distance greater than
the mean orbital distance of Jupiter from the Sun (5.2026 astronomical units [AU])
and a semi-major less than that of Neptune. (Several Centaurs exceed the semi-major
axis of Neptune. Recent astrological consensus implies that if the semi-major axis is
less than or about that of Pluto—39.537 AU—then the object could still be consid-
ered a Centaur). The Kuiper Belt consists of a yet undetermined number of objects
made up of frozen gas and dust that orbit in the general vicinity of Pluto and Neptune.
Astronomer Gerald Kuiper initially speculated about the existence of the Kuiper Belt
in the 1950s.
THEASTROLOGYBOOK [131]
CentaursA diagram of the celestial sphere from Orontius Fine,
c. 1542. Reproduced by permission of Fortean
Picture Library.