Rahu and Ketu
Ketu is the oldest among all grahas followed by Rahu. They both represent the mysteries of life and its existence. Rahu is the mystery you are yet to discover and Ketu is the mystery you discovered already in your previous lives.
Rahu, the north node (aka head of the serpent) and Ketu, the south node (body/tail of the serpent). Rahu and Ketu are non-physical/shadow planets and will be visible only at the time of solar and lunar eclipses. Their positions are calculated based on the path the Sun and Moon takes around the earth over the course of a year. If you take earth as a stationary object (from an observer's view) you can imagine the Sun and Moon’s path criss-crossing each other several times a year through two junction points which are called the nodes. The Moon’s orbit crossing over the Sun’s orbit from south to north is called Rahu (north node) and from north to south is called Ketu (south node). Everything north is considered as Rahu’s domain and everything south is considered as Ketu’s domain.
Lord Rahu and Ketu
Rahu and Ketu are basically the head and body/tail. The beginning and the ending. Rahu and Ketu were together once as one head and body and they were called “Swarbhanu”, the only asura who was given the status of a planet. Long story short, Swarbhanu was highly talented and gained ashta siddhis (eight magical powers). He also gained the status of a planet from Lord Brahma through his severe penance. But even after all this, he couldn't control his asuric tendency (shadripu) at the time of churning of the ocean (to get the amrit). He tricked everyone into believing that he was one of the devas to drink the amrit (divine nectar) of immortality first. Lord Vishnu watching this didn't say anything. Swarbhanu drank his share but everyone found out and prayed to Lord Vishnu to kill him for his wrongdoing. Vishnu then cut his head off but Swarbhanu did not die as he took his share of amrit already. The life energy of Swarbhanu was still there but his body became doubled (one reality split into two). Lord Vishnu took a serpent and attached its head to Swarbhanu’s body (Ketu) and its tail to Swarbhanu’s head (Rahu).
This teaches us a great philosophy that everything beautiful, peaceful, comfortable and long-lasting in life starts with a violent energy.
Rahu signifies the future, modern technology, modern society, foreign things, western world, macrocosm, rumours, excessive eating, distraction, macro organisms, giant animals, cats etc. as intangible significations. Tangible significations are paternal grandfather and maternal grandmother, foreign friends & contacts, islam etc.
Ketu signifies the past, ancient technology, ancient society, local things, eastern world, microcosm, hearsays, excessive fat in the belly, traction, micro organisms, small animals, dogs etc. as intangible significations. Tangible significations are paternal grandmother and maternal grandfather, local friends & contacts, priests & monks etc.
Both the nodes give sudden results but Ketu is faster and stealthier than Rahu as it has the head of a serpent. Rahu is known as the bhoga karaka (significator of abundance) and Ketu is known as the moksha karaka (significator of liberation). So usually, what Rahu gives you will be taken away by Ketu and vice versa. Apart from that they both signify time. Rahu’s position in your chart will tell you where you’re heading (future) and Ketu’s position will tell you where you were before (past events including past lives). Rahu’s position shows your eagerness to gain knowledge regarding its house, sign and nakshatra. Ketu’s position shows your eagerness to teach regarding its house, sign and nakshatra. All your other planets are helping your nodes through their own ways in order to push you towards your future. They feed the nodes throughout the journey. They feed through different ways. First they’ll do it based on the relationship they have with your nodes. For ex., if your nodes are friendly with most of the planets (which it does under certain conditions) then it’ll be easier for your nodes to feed on and move ahead. Second way is through the transiting planet over your Rahu and Ketu. For ex., if Jupiter is going over your natal Rahu then it’ll feed your Rahu with guidance and wisdom (good/bad based on its position and relationship) related to the house it is placed in. Third way is through nodal transit. It means the node itself goes over your natal physical planets. It's a bit tricky as sometimes it feeds on even the immature karma due to its hungry nature. For ex., Rahu going over a strong Mars and Venus conjunction can spark the romantic energy of the native but if Mars and Venus are weak then it can burn the energy to its emptiness.
Rahu and Ketu represent no gender. They mature at the age of 42 and 46 respectively. It's the midpoint of life when you get the full understanding of your past, present and future. Rahu is connected to numbers 4 and 36. Ketu is connected to numbers 7 and 39.
Rahu gets exalted in Taurus and debilitated in Scorpio. Ketu gets exalted in Scorpio and debilitated in Taurus.
Rahu co-rules the sign Aquarius. Ketu co-rules the sign Scorpio.
Rahu’s favourable direction is south-west and Ketu’s favourable direction is north-west.
Rahu is friendly with Venus, Mercury and Saturn. Ketu is friendly with Mars and Jupiter.
Rahu and Ketu are enemies with Sun and Moon.
Rahu’s associated colours are UV, all shades of blue/brown and electric blue. Ketu’s associated colours are infrared, all shades of grey.
Rahu is mostly resembling the Sun, Ketu is mostly resembling the Moon.
Rahu’s ruling deity is Goddess Durga and Ketu’s ruling deity is Lord Ganesha.
Rahu represents air (vayu), Ketu represents fire (agni).
Rahu Ketu Philosophy
Time isn't linear but cyclical and we’re just time travellers. That's what the nodes denote through the image “Ouroboros”.
Rahu follows Ketu and vice versa. History repeats itself through time. Past becomes the future and vice versa. Time should be cyclical and that's why Lord Vishnu let Swarbhanu drink the nectar otherwise the cycle of birth and death, victory and defeat, gain and loss, happiness and sadness will not exist in the first place. Rahu and Ketu teaches us the duality of nature. Rahu becomes the cause of Ketu while Ketu becomes the cause of Rahu. They are the polar opposites outwardly but always connected to each other mysteriously (connected to each other in higher divisional charts). This is why they both are always seven houses away from each other. 7th house from any house is direct opposite to that house thus it represents everything opposite. For ex., you're your 1st house and your partner is your 7th house. You and your partner are opposite in many ways yet connected through the bond of marriage. This is how Rahu and Ketu are. They compensate each other by balancing each other's energies as remedies.
"We drive into the future using only our rear view mirror"
It also shows that 7th house from any house becomes the balance of that house. This one philosophy is enough to find balance in any part of life. And that's why understanding the nodes are most important.