What other Researchers Never Answer - 9

Rahu-Ketu and Eclipses 

Sun and Moon are the two large objects we regularly see on our skyline. Earth coming around Sun in an elliptical path. Moon comes around Earth in elliptical path.

A Lunar Eclipse happens when the Earth, Sun and Moon align in space, with Earth in between the Sun and Moon. At such times, Earth’s shadow falls on the Full-Moon causing a Lunar Eclipse.

A Solar Eclipse happens at the opposite phase of the Moon  New-Moon when the Moon passes between the Sun and Earth. 

Why there aren’t Eclipses at every Full and New-Moon?

The Moon takes about a month to orbit around the Earth. If the Moon orbited in the same plane as the Earth’s eclipticorbital plane, we would have two Eclipses every month. 

However, the Moon’s orbit is inclined to Earth’s orbit by about 5°. Twice a month the Moon intersects the ecliptic – Earth’s orbital plane at points called nodes. If the Moon is going from south to north in its orbit, it has called an ascending node.If the Moon is going from north to south, it is a descending node. If the Full-Moon or New-Moon is appreciably close to one of these nodes, then an Eclipse is not only possible, but also inevitable.

The ascending node is called as Rahu, and the descending node is called as Ketu in Indian astrology. Rahu and Ketu are fittingly named as shadow planets, as these nodal points are shadows of Earth and Moon.

Though Sun is very big and Moon very small comparatively, their distance from Earth also very different. Moon is approximately at 4 lakhs Km distance from Earth and Sun is at 15 crore Km. Hence approximately both will be seen as similar in size from Earth.

Because the orbital plane of the Moon precesses in space, the lunar nodes (Rahu & Ketu) also precess around the ecliptic, completing one revolution (called a draconic or nodal period) in 18.612958 years. These nodes travel in the opposite direction of other planet movements.  

A Lunar Eclipse can occur only when the Moon is near (within 11° 38' ecliptic longitude) either lunar node (Rahu & Ketu) and during a Full-Moon. In Hindu astrology, the Lunar Eclipse occurs when Sun is near to Rahu or Ketu and Moon crossing the other shadow planet. 

Rahu grahasta Lunar Eclipse: Sun would be in Ketu node. In addition, when Moon crosses the Rahu node Eclipse will occur.

Ketu grahasta Lunar Eclipse: Sun would be in Rahu node. In addition, when Moon crosses the Ketu node Eclipse will occur.

A Solar Eclipse can occur only when the Moon is near (within 17° 25') either lunar node during a New-Moon.

Rahu Grahasta Solar Eclipse: Sun would be in Rahu node. In addition, when Moon crosses the Rahu node Eclipse will occur.

Ketu Grahasta Solar Eclipse: Sun would be in Ketu node. In addition, when Moon crosses the Ketu node Eclipse will occur.

During lots of months Sun and Moon don’t align with Rahu and Ketu during New-Moon and Full-Moon days. Those Amavasya and, Purnima days Eclipses won’t occur.

A better representation of Sun-Earth-Moon view could give a better understanding of above illustration. 

Vedic astrology, Rahu and Ketu have an orbital cycle of ~18 years and are always 180° from each other. The precessional orbit of Moon has approximately 18-year rotational cycle of the lunar ascending and descending nodes on the Earth’s ecliptic plane. This also corresponds to a saros, a period of ~223 synodic months (18 years, 11 days, 8 hours), that can be used to predict Eclipses of the Sun and Moon.

Often during Sanskrit to English translation, scholars mistake Ketu as Neptune. However, Neptune is not visible to the naked eye and its discovery is attributed to the use of high-resolution telescopes in modern astronomy. Here in Mahabharat also Vyasa describes Ketu as “śyāmo grahaḥ dhūmaḥ saha” i.e “The black planet, blazing up like fire mixed with smoke”.