Introduction to Celestial Bodies – 1:[1]
Types; Apparent Size in Relation to Sign Cusps

– written by Philip Graves Feb 05 2003
– reformatted for WordPress, June 3rd-4th 2016

There are various celestial bodies (large conglomerations of physical matter outside the Earth) which by their position and direction of travel on a north-south scale in relation to the equator of the Earth, as measured in signs and degrees longitude of the tropical zodiac, yield sign placement information; and which by the positional relationship between their zodiac sign and degree placements, on the one hand, and the projected placements within the zodiac of the angles or cardinal points and intermediary house cusps at particular locations on the Earth’s surface, which change in a complete cycle on a daily basis with its axial rotation, on the other hand, yield house placement information.

Each celestial body has its own characteristic blueprint of radiation which impacts upon everybody existing on the Earth in general, and upon those located at particular points on its surface, in a different fashion at different times in accordance with its sign placement and house placement (respectively).

Depending on the nature of this characteristic radiation blueprint, each celestial body has been observed to have a general influence on certain features of human personality and physiology, as well as upon events in relation to their lives. This influence is then channeled through the filter of the signs and houses it occupies, and is modified and expressed in the manners and areas of life they indicate. It is also moderated by the angular relationships (measured by degrees arc of separation) between the direction from which the radiation of the celestial body concerned is approaching the Earth and the direction from which the radiation of each other significant celestial body is approaching the Earth. These angular relationships, where significant in their moderating influences by nature of their angular geometry, are known as aspects.


Types of celestial bodies

Celestial bodies are classified according to their astronomical function, location and size into stars, planets, planetoids, asteroids, and moons.


The Stars

A star is a vast burning mass of matter, which serves as an extremely powerful source of radiation, including light frequency radiation and heat energy. It is mostly composed of the plasma state of matter since its temperature is much too high for it to be a gas.

In astrology, the star orbited by the Earth is of primary significance. It is known as Sol or the Sun. The Earth orbits the Sun once every 365¼ days, this unit of time being popularly termed a year. The incline of the Earth’s plane of orbit around the Sun (the ecliptic) to its spinning axis (equator) is the basis of the zodiac signs; and as the Earth moves around the Sun over the course of each year its sign placement correspondingly changes in a full annual cycle.

There are many other stars whose light radiation is distinctly visible from Earth. Since the Earth does not orbit them, their apparent motion is virtually zero, and to most intents and purposes they are regarded as fixed at particular sign and degree placements in the zodiac. They are therefore collectively known as the Fixed Stars. They do however apparently advance through the zodiac at a rate of about 50.3″ per year, every approximately 71 years, 213 days, or one tropical sign every 2147.5 years. And their complete circuit of it, which lasts an estimated 25,770 years, is a cycle known as the precessional year or great year.

The astrological influence of the fixed stars is confined to their positioning in close conjunction (no more than two degrees’ orb allowed) or parallel (no more than one degree) to the angles, luminaries and planets in the birth chart. All other aspect types, as well as sign and house placements, are considered immaterial. Although astronomers have sought to group fixed stars together into constellations, these groupings are entirely arbitrary divisions representing the relative positions of the fixed stars as viewed from Earth, and have no unitary significance as agents, unless one subscribes to the tenets of sidereal astrology. From a western (tropical) astrological perspective, only the individual stars in isolation from the constellations into which human beings have grouped them are considered significant.


The Planets

Planets are smaller but still substantial bodies of matter which are not such significant sources of heat energy or light frequency radiation than stars, but are heated by the stars they orbit to varying degrees, depending substantially upon how closely they are located to them, as well as atmospheric properties. They are gravitationally locked into orbits around stars. Our star, Sol, attracts eight celestial bodies universally recognised as being planets, listed here in ascending order of their mean distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. These planets and all the other bodies of matter orbiting Sol are known together as the Solar System.

The inferior planets are those within Earth’s orbit of the Sun: Mercury and Venus. The superior planets are those outside Earth’s orbit of the Sun. The inner planets (those within the asteroid belt’s orbit of the Sun) are Mercury, Earth, Venus and Mars. The outer planets, all of which are gas giants, are Jupiter, Saturn, Uranus and Neptune.

Planets are sources of invisible radiation on a less dramatic scale than stars, and also reflect a certain fraction of the visible and invisible radiation of the Sun from their surfaces. Strictly speaking, the Earth is not a celestial body since the term ‘celestial body’ refers from a geocentric (Earth-centred) perspective to all bodies in space external to the Earth. Astrology is interested in how celestial bodies relate to the Earth, and the effects of these relationships upon life.


The Planetoids

Planetoids are in effect small planets, varying in their regularity of form and path, which orbit a star like planets but are tiny by comparison with them. Any small celestial body which orbits the Sun outside the asteroid belt is classed as a planetoid. The best-known planetoids for which ephemerides have been computed occur in two areas of the Solar System. The nearer is the region between the orbits of Jupiter and Neptune. All planetoids located here are collectively known as centaurs. They include Chiron, Pholus and Nessus. The farther is the region beyond the orbit of Neptune, which is termed the Kuiper Belt. All planetoids located here are termed Kuiper Belt Objects. By far the largest to have been discovered so far is Pluto. Others of some lesser significance include Varuna, Ixion and Quaoar.


The Asteroids

Asteroids are a very large number of tiny planets orbiting the Sun between the orbits of Mars and Jupiter. By far the largest is Ceres. The second to tenth largest, all with diameters over 250km, are in descending size order: Vesta, Pallas, Hygiea, Davida, Interamnia, Europa, Eunomia, Sylvia, and Psyche. Asteroids which cross beyond Jupiter for part of their orbit are termed Trojans.


The Moons

Moons (or satellites) are bodies of matter which orbit not stars but planets (or even planetoids) but in terms of material composition may be generically indistinguishable from planets. Only some planets have Moons. The Earth’s Moon is called Luna or simply ‘the Moon‘. In astrology, Sol and Luna are collectively known as the Luminaries or the Lights. This is because, although our Moon is not a source of light, it reflects a substantial amount of the Sun’s light very visibly to us. Jupiter has 17 Moons. Saturn has 28 Moons. Uranus has 21 Moons. Neptune has 11 Moons. Pluto has one known Moon, called Charon, which is over half its diameter. The Moons of these other planets are of no known astrological significance because their orbits are so close to the planets from a geocentric perspective as to be positionally indistinguishable from them, although they are sure to exert some unassessed modifying influence on the nature of the radiation received by Earth from their parent planets, in accordance with the angular relationship between the Moon concerned and Earth from the perspective of this Moon’s parent planet.


Apparent size of celestial bodies, in relation to sign cusps

As viewed from Earth, the different celestial bodies have different apparent diameters measured by minutes and seconds of arc, which vary during the course of their cycle through the zodiac from the maximum apparent diameters attained when they are at their closest distance from the Earth, which is called perigee, to the minimum apparent diameters attained when they are at their farthest distance from the Earth, which is called apogee. Since the Earth orbits the Sun and is orbited by the Moon, its distance from both of them remains relatively constant; but its distance from the other planets is much more drastically variable.

When any celestial body is situated at the crossing point or cusp between two zodiac signs, for a certain period of time it will be partly situated in both signs, this length of time increasing in direct proportion to apparent diameter and in inverse proportion to speed of motion. When a celestial body is partly in two signs at the time of birth, it will exert some of its characteristic general influence through the filters specific to both signs. To determine whether or not any celestial body may truly be partly on the cusp between two signs, first of all calculate the distance in minutes and seconds of arc separating the position of the centre of the body from the exact position of the cusp between the signs. There are sixty seconds (“) to every minute (‘), sixty minutes to every degree (º), and thirty degrees to every sign. Thus, for instance, the Sun at 29º54’22” Taurus is 5’38” from the cusp between Taurus and Gemini. Then divide the apparent diameter of the celestial body concerned by two to find its apparent radius, which is the distance between its centre (whose position is known) and its outermost edge. If the apparent radius exceeds the distance separating the centre of the body from the cusp, then part of the body is in the next sign, and some of that sign’s influence can be expected.

The following table shows the mimimum and maximum apparent diameters, in minutes and seconds of arc, for the luminaries and planets, including Pluto; and then their minimum and maximum distances from the Earth, in millions of km.:

   Apparent Diameter   Distance from Earth
 Minimum  Maximum   Minimum   Maximum
Sun 31’27.00″ 32’31.00″  147.0900  152.1000
Moon 29’22.00″ 33’31.00″    0.3633    0.4055
Mercury     4.50″    13.00″   77.3000  221.9000
Venus     9.70″    66.00″   38.2000  261.0000
Mars     3.50″    25.70″   54.5000  401.3000
Jupiter    29.80″    49.00″  588.5000  968.1000
Saturn    14.50″    20.10″ 1195.5000 1658.5000
Uranus     3.30″     4.10″ 2581.9000 3157.3000
Neptune     2.20″     2.40″ 4305.9000 4687.3000
Pluto     0.06″     0.11″ 4293.7000 7533.3000

NB: In order for the tables on this page to display properly in WordPress, it was necessary to add zeros to some figures after the decimal points. These are not significant figures.

It should be apparent from this table that the cusps may come into play when the centres of the planets are no further than 33″ (Venus), 24.5″ (Jupiter), 12.8″ (Mars), 10.0″ (Saturn), 6.35″ (Mercury), 2.05″ (Uranus) or 1.2″ (Neptune) away from them – and these are the maximum figures for when the apparent diameter of the relevant planet is at its greatest, the average being considerably less in each case. The occurrence of a planet within such tiny fractions of a minute of a degree of a sign cusp is very rare, so a planet being on a sign cusp can be safely disregarded as a possibility unless by its recorded position it is clearly within half a minute (1/120 of a degree) of the cusp – and even then nothing is definite unless it falls within 50% of the minimum values for the apparent diameter.

However, there is a much more significant extent to the apparent radius of the Sun and Moon. When either is centred within about 15 minutes, or a quarter of a degree, of a sign cusp, part of its diameter will most probably extend into the adjacent sign.

Since the rate of motion of the Sun is approximately 59 minutes arc per day, and its mean apparent diameter 32 minutes arc, it takes approximately thirteen hours, or just over half a day, for the Sun to completely change signs; therefore anybody born within about 6½ hours of the Sun’s ingress time into a new sign will be subject to the influences of both signs.

The rate of motion of the Moon is approximately 12.2º arc per day, and its apparent diameter about 31’26”, or 0.523º, it will travel by the arc of its own apparent diameter roughly 12.2 / 0.523 = 23.3 times a day, and therefore the time it takes to cross a single point such as a sign cusp will be 23.3 / 24 = 0.97 hours, or 58 minutes and 10 seconds. Therefore, anybody born within about 29 minutes of the Moon’s ingress time into a new sign will be subject to the influences of both signs.


Continue To Part Two of Two…


[1] NB: This article was written at the age of 28 from the theoretical standpoint of postulating a physically causal model of astrology. It is readily acknowledged that such a model is not accepted by the majority of astrologers today and was not accepted by the majority of astrologers in 2003 either. I nonetheless feel it was a useful exercise in bringing issues of reason and relative measurements to the table in the consideration of how and why astrology may work in the objective world.

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