Rahu, the North Node, is assigned the rulership of the sign Aquarius by the sage Parashar, who is one of the prime contributors to the richness of Vedic astrology.

Rahu has a nature very similar to that of Saturn, so it can rule either Capricorn or Aquarius.

But since it is airy in temperament and is a mystical planet, it automatically qualifies for the co-rulership of Aquarius.

According to ancient Indian mythology, Lord Shiva (the god of destruction and one of the trinity) is supposed to preside over the sign Aquarius.

He is blue in color, has matted locks with holy waters flowing from them, wears a snake around his neck, is unmindful of his appearance, and roams around the snow-filled mountains.

So it is not hard to see the obvious connection between his physical and mental attributes and those of Aquarius.

He has blue color; Aquarius is the sign associated with blue color in both Vedic and western astrology.

He is unmindful of his appearance and has matted locks; Aquarius is the most ascetic among the signs, and people with Aquarius strong or Aquarius rising are the least mindful about their looks.

Roaming around the snow-filled mountains shows the ascetic nature of Shiva, which is the very nature of Aquarius.

Pisces, the last sign in the zodiac, is the sign ruling complete wisdom and liberation. Now, true wisdom and liberation are only possible after renunciation of the material world.

Aquarius is the sign preceding Pisces, and thus rules that penultimate stage in the journey of man toward liberation.

Now the question arises: What connection does the snake (representing the serpent power) have with Aquarius? That's where Rahu comes into the picture.

The knowledge and wisdom associated with Aquarius are not attained until one masters the Kundalini Shakti (the coiled serpent power), which resides in every human being at the sacrum bone at the base of the spine.

Among the planets, Rahu represents this serpent power. (Rahu also presides over the color blue, signifying Aquarius.)

Mercury and Rahu also have a close relationship, and Rahu is assigned the part rulership of Virgo in various texts of Vedic astrology.

Rahu represents the deeper, and sometimes dark, side of the intellect, which is ordinarily governed by Mercury.

Both are planets of knowledge, with Rahu ruling over the intuitive knowledge.

Rahu is often the force behind a genius who turns to criminal ways, as it is responsible for the perversion of the intellect.

Rahu is a trickster in the same way as Mercury is, but is usually more magical in its approach and dangerous in its intentions.

In fact, Mercury always has some bit of Rahu in it, even when it is not connecting with Rahu in a particular nativity or birth chart.

The ancient Indian mythological deity ruling Mercury is Lord Vishnu (one of the trinity, with the function of preservation). He is always seated on a serpent, which separates him from the ocean of illusion (the phenomenal world).

This points toward the close association between Mercury and Rahu, as well as the fact that one cannot transcend the material realm without mastering the forces of illusion, fears and temptations that Rahu seems to represent.

Thus, though many other viewpoints exist, it would be safe to say that Rahu is the co-ruler of Aquarius and Virgo as per Vedic astrology.

It is exalted in Scorpio, and also behaves well in Virgo, Cancer and Sagittarius -- though this is a guideline, and is not to be applied blindly.

It is very difficult to predict whether Rahu will work on its higher principle (true knowledge) or its lower principle (illusionary power) in a particular nativity. Much depends on the overall spiritual advancement of a soul, because Rahu is the planet that separates the sages from the ordinary mortals.

Since Vedic astrology does not use the outer planets, their attributes are usually assigned to the nodes (Rahu and Ketu).

Rahu is sort of Uranus, Neptune and Pluto combined together. It is supposed to combine the shocking revolutionary power of Uranus with the almost hallucinatory and sensitizing influence of Neptune. It also covers the dark underworld side of Pluto.

It is supposed to be the planet of inspiration, giving rise to sudden inventions and discoveries. Rahu is thus the planet which has made its influence felt most strongly in the 20th century.

Also, in western astrology, Rahu's influence is seen to be equivalent to Jupiter and Venus combined, and it often correlates with Jupiter as a point of easy expansion of energy, leadership potential, and good luck.

It is seen to improve the results of the house in which it is placed. But this, though not entirely false, is not a true picture of Rahu. Rahu can behave in a positive Jupiterian manner only under certain conditions.

This happens only when it is placed in strong houses like the first, ninth, and tenth, and aspects or is conjunct with the important planets in that particular chart.

It also helps if Rahu is in its own sign, exaltation sign or the signs it is comfortable in. Rahu has an expansive nature -- but at the same time, it can be a disintegrating, rather than a creative, influence if these conditions are not satisfied.

Rahu is capable of giving highly malefic results, especially when placed in malefic houses and aspecting or conjunct with malefic planets in a particular nativity.

Uranus is supposed to be the co-ruler of Aquarius in Western astrology.

It is considered the planet governing the new developments in electronics, space and atomic research. In Vedic astrology, Rahu has been seen to be the signifier of electricity in all its forms (lightning, etc.) and thus responsible for these advances.

Rahu and Uranus have a lot in common, but Rahu behaves in a totally Uranian way in a nativity only when it is strongly related to Uranus by aspect or conjunction. The Rahu-Uranus conjunction is quite important, as it produces inventors, researchers, and generally people with radically different ideas in various fields.

Neptune is supposed to be the co-ruler of Pisces, along with Jupiter. It is considered to be the psychic side of Jupiter, and the planet of imagination, illusion, fantasy, and charm.

Though Rahu possesses these qualities in some measure, it requires some relationship with Neptune in a horoscope to fully reflect these qualities. The Rahu-Neptune conjunction is good for producing musicians, mystics, etc.

Any association of Rahu with Pluto in the horoscope gives some special power in a specific area, depending on the nature of the houses involved.

Whether this power will be used destructively or constructively depends on other factors in the chart. So, it is clear that Rahu is deeply influenced by the planets it is related with in the nativity. This characteristic of Rahu is similar to that of Mercury.