Shadbala (six-fold strength) is a method in Indian Astrology to find the strength of planets. Natural strength of planets is one of the strengths in shadbala. This strength is fixed and holds well in all nativities. The strength of planets in birth chart always leaves impact on the personality of the native. Thus, the question arises, when it is constant for all the horoscopes, why it should be included in the shadbala? The predictive results have also been given in the classical books: –
Dr. B. V. Raman in his book ‘Graha and Bhava Balas states ‘that the value assigned to each planet depends upon its luminosity’.
It is a well-known fact that the planets have no light of their own but reflect the light received from the Sun. Now we shall discuss the luminosity (The light received on the earth) of the planets as per modern astronomical facts. Before proceeding to it, let us see how the luminosity varies from time to time depending upon their distance from the earth.
Magnitude (Brightness) of Inner planets
Phases of inner planets (Mercury and Venus) are like moon. Refer to figure given below:-
Sun is at the center of the orbits of the inner planet and the earth. An inner planets position at different times is shown in the circular path and bigger are shows the path of the earth. Inner planet appears full when it is at H and circular disc is visible but it is at the maximum distance from the earth. It appears more than half at D and I, as more than half the bright disc is towards us. At C and J only half the lighted disc is visible at the Earth. At B & K less than half the illuminated position is facing us, so it appears less than half. At A its dark side is been by us, so it is not visible at all, though it is nearest to us.
Phases Of Superior Planets
The superior planets must always appear either full or gibbous; for its orbit is outside orbit of the earth. It appears full at conjunction or opposition. Its illuminated disc is always more than half towards the earth. The smallest portion of the planet will be seen when the sun and the planets subtend a right angle at earth.
Brightness (Magnitude) of the planets
The amount of reflected light received from a planet at the earth is the brightness of the
Planet / Star. This reflected light is based on based on two things: —
(A) If the distance of a planet from the earth is more, light received from it will be less and the planet becomes brighter as it reaches near the earth. Brightness of light is inversely proportional to the square of its distance from the earth. If a source of light goes three times away than its earlier distance, the magnitude of light will be one-ninth of the original one.
(B) It depends also on the portion of the illuminated disc of the planet towards the earth. If more illuminated portion of the disc is towards earth, more light will be received on the earth.
Magnitude Of Inner Planets
We consider the case of Venus. When it is at superior conjunction, it is at maximum distance from the earth and at inferior conjunction it is at the least distance. Diameter of its disc is 11” at superior conjunction and 66″ at inferior conjunction or 6 times more than superior conjunction. At the time of inferior conjunction, a very small part of its illuminated disc is towards the earth or visible to the observer, while at superior conjunction the whole disc is normally visible. When elongation angle of Venus (the angle subtended by the sun and the Venus at the earth) is 40°, the brightness is at maximum.
Magnitude Of Outer Planets
An outer planet at the time of opposition appears like a full moon. The whole disc is visible and it is nearest to the earth. While at conjunction, though the whole disc is normally visible but it is at the maximum distance from the earth, its disc appears smaller also. In between these two positions, at quadrature (the angle subtended by the planet and the sun at the earth is 90) it appears most gibbous.
Maximum Magnitudes Of Planets are as under: –
Moon (-) 12.7
Mars (-) 2.8
Mercury (-) 1.9
Jupiter (-) 2.6
Venus (-) 4.4
Saturn (-) 0.3
The greater is the magnitude, lesser is the brightness. Planets with minus magnitude are brighter than the positive ones.
In case we take Saturn as 1, Moon 42.3, Mars 9.3, Mercury 6.3, Jupiter 8.7 and Venus 14.7 times brighter than Saturn. But this brightness varies as per their distance from the earth. Take the case of Mars which looks like a star at the time it is farthest from earth. Similarly, is the case with Jupiter and Saturn. Regarding inner planets Mercury and Venus, it has been discussed earlier.
It is concluded that their luminosity varies. Hence the natural strength needs to be removed from the Shadbala of Grahas or another formula depending on their angle of elongation and distance may be found out.
There are many things in Astrology that was taught earlier which requires modification according to the modern knowledge of Astronomy for which a team of Science and Mathematics experts is required who are also well versed in astrology.