What are the Navagraha?
The navagraha are the nine grahas — literally “seizers” — that Indian astronomy tracks along the zodiac: Surya (Sun), Chandra (Moon), Mangala (Mars), Budha (Mercury), Guru (Jupiter), Shukra (Venus), Shani (Saturn), and the two lunar nodes Rahu and Ketu.
Seven visible, two shadow
The first seven are bodies you can see, and they name the seven weekdays in Sanskrit exactly as they do in Latin. Rahu and Ketu are not bodies at all: they are the two points where the Moon’s orbit crosses the ecliptic. That is why eclipses can only happen near them — the classical image of Rahu swallowing the Sun is a description of that geometry.
Rahu and Ketu are always opposite, always retrograde
The two nodes sit exactly 180° apart by definition, and the node line drifts backwards along the zodiac, completing a circuit in about 18.6 years. So Rahu and Ketu are always shown retrograde, and always in opposite rashis — a property no physical graha has.
Retrograde and combustion
Mangala, Budha, Guru, Shukra and Shani periodically appear to move backwards against the stars (vakri, retrograde) — an effect of the Earth overtaking them or being overtaken, not a real reversal. A graha too close in longitude to the Sun is called asta (combust) and is traditionally read as weakened. Surya and Chandra never retrograde.
What a chart records
For each graha a kundali records the sidereal longitude, the rashi and nakshatra containing it, the pada, and whether it is retrograde or combust at that moment. Those are measurements; the classical significations attached to them are interpretation.
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FAQ
Why are there nine grahas and not eight or ten?
Seven are the visible Sun, Moon and five planets; Rahu and Ketu are the two lunar nodes. Uranus, Neptune and Pluto are not part of the classical scheme, being invisible to the naked eye.
Are Rahu and Ketu real planets?
No. They are the intersections of the Moon’s orbit with the ecliptic — mathematical points, which is why they are called shadow grahas and are always exactly opposite each other.
What does retrograde (vakri) mean?
That a graha appears to move backwards through the rashis as seen from Earth. It is a perspective effect of two orbits, not an actual reversal of motion.