Dear TBs Sir,
Rahu and Ketu are actually the northern and southern nodes of Moon. For that matter Sun and Moon are also not Planets. So we are left with Mercury, Mars, Jupiter, Venus & Saturn. Of course Earth is left out being the point of event. But astrology believes these the planets along with Sun & Moon could impact the events on earth and hence is considered as Graha ( some thing which has the power to grab or hold). One of the text in Jyotisha gives description Rahu/Ketu like this.
RAHU and KETU (the nodes of the Moon)Rahu and Ketu are not physical planets; they don’t have a physical mass, but are very powerful energetic points in the sky. They are the points of intersection between the path of the Sun and the path of the Moon, causing the solar and lunar eclipses. They are very important on the spiritual level, as they are related with the unconscious shades, unresolved karmas and conflicts coming from previous lives. They are mythologicaly represented by a snake that was cut in two: the head (Rahu) and the tail (Ketu). This inner conflict manifests as two antagonistic, opposite forces in the sub-conscious mind that generate conflicts, dualities, fears, compulsive desires, rejections or phobias, and karmic situations which lead us to face them and work them out.
When we can understand and connect those two antagonistic forces, the “Kundalini”—the inner spiritual power and strength—awakens, leading to inner healing, peace of mind and spiritual illumination.
Therefore, Rahu and Ketu can be the cause of great conflicts, dissatisfactions and diseases, but by understanding and working them out spiritually, we can connect them and transform them into a great spiritual power.
RAHU – (the north node)
Rahu is related with the unconscious desires, dissatisfactions, fears, obsessions, ambitions and unresolved issues from previous lives that need to be experienced in this life. The houses and signs where Rahu is located indicate areas where there will be mental restlessness, hypersensitivity, strong desires to experience that area, but fears to do so and dissatisfaction with it at the same time.
It tends to create very strong but unconscious desires, without really understanding their causes, which can lead to compulsive behavior, addictions, fantasies, unrealistic imaginations or suggestions.
Rahu represents the unconventional, illegal, dark but desired; also foreigners, people out of the social system and its norms, or “outcasts.” It can also be transformed and sublimated into a spiritual energy, knowledge of the occult side of the mind, or knowledge of psychology. Understanding and control of this energy leads to esoteric knowledge and awakening of the Kundalini power.
KETU – (the south node)
Ketu is represented by a Sadhu, a mendicant ascetic monk, one who rejects the world and its vanity, instead looking for the essential truth alone. Ketu indicates areas where detachment has to be developed, areas that will be the source of some suffering—with the purpose of being spiritualized, searching for life’s very essence. Ketu is considered a very important planet for spiritual evolution, because it represents the capacity for renunciation, detachment from the ephemeral, and a search for the truth and the essence of life. It also represents Moksha, liberation from the cycle of births and deaths and attainment of illumination.
A predominant Ketu can be seen in the charts of monks, ascetics, renunciates, and psychic and clairvoyant people.
The placement of Ketu in the birth chart indicates areas that have been experienced in excess in previous lives, now causing feelings of dissatisfaction and rejection towards them.
Ketu can cause damage and restrictions in the areas it affects, but it is also a way of spiritual learning.
An adverse Ketu can cause ruptures, breaks, accidents or diseases, but alternatively it can bestow intuitive knowledge coming from past life experiences.
There references of Rahu Ketu in Puranas as well in Mahabharata the third canto of Bhishma parva says
अभीक्षम कम्पते. भूमिरर्क रहुस्त्था ग्रसत
श्वेतो ग्रहस्तथा चित्रां समतिक्रम्य तिष्तती
considering these, we have enough evidence to believe that the Rahu/Ketu were part of vedic era as well.
In another place in Bhishma Parva these quotes appear
कृत्तिकासू ग्रहस्तिर्वोन्क्शे प्राथमे ज्वलंन
वम्पूश्यपहरन भासा धूमकुतुर्रवि स्थित:
This suggests that at the time of Mahabharata War, a planet was present in Krittika Nakshtra, by reverse calculation, we have now established that the planet was Pluto. Various researches are going on to prove the existence and the effects of pluto in our astrological system which are at quite advanced stage.
As an astrologer, I would not advice this. Sorry.