Rahu and Ketu are known as North node and South node in astronomy, these are not a real planet but calculated points in the universe.
Calculation of Rahu and Ketu
There is an orbital plane of Earth around the Sun, Moon rotates around Earth in a circular fashion, so Moon intersects the plane of Earth and Sun at two points. These points are calculated using the projected path of the Moon around Earth, these are called Rahu and Ketu.
You can look at the below diagram for easy understanding.
- Rahu (North Node) – It is known as an ascending point when Moon crosses from downward to the upward side of the plane.
- Ketu (South Node) – It is known as a descending point when Moon crosses from upward to the downward side of the plane.
Role of Rahu and Ketu during an Eclipse
The moon completes the cycle of rotation around earth in 28 days, so the moon, earth, and sun all align two times in 28 days but why there is no eclipse? ….confused
Look at the below figure.
The line connecting two Rahu and Ketu is known as lunar nodal axis or line of nodes
In this figure, you can see that Sun, Moon, and Earth aligned but still, there is no eclipse as the nodal axis or line of nodes is not aligned. They are in a single plane but not in a single line.
They align two times in 28 days in a single plane but not in a single line.
This is the second figure, where Moon, Sun, and Earth are all aligned in a row and the nodal axis is also aligned.
Here all the three are aligned in a single line, Moon has taken the position of Rahu and shadowed the light of Sun.
Hindu Mythology has defined this phenomenon in a very unique way describing Rahu as a headless entity (devil) who swallows the Sun at the time solar eclipse (Surya Grahan). There is the whole story behind it coming directly from Vishnu Purana.
The same happens while Lunar Eclipse (Chandra Grahan), Moon takes the position of Ketu and hence Earth blocking sunlight to Moon and on that day instead of Full Moon (Purnima), you see the shadow of the earth on Moon.
On the day of the eclipse, Earth experience the highest gravitational pull both from Sun and Moon as they are aligned in the same line. So there is a high tide in sea level. This also happens on New Moon (Amavasya) and Full Moon (Purnima) but as I said earlier they are not aligned in line but on a plane, so the level of gravitational pull is lower than eclipse but higher than normal days.
Rahu and Ketu in Birth Chart
1) Rahu and Ketu are always placed opposite to each other and they form an axis in the birth chart.
2) If Rahu and Sun are together in one house, your birth date is near to a Solar Eclipse. If all the three planet Rahu, Sun and Moon are in a single house, then your birth date and time is very closer to Solar Eclipse (Surya Grahan).
3) If Ketu is with Moon in any house and Sun is with Rahu, you must have born near to Lunar Eclipse (Chandra Grahan)
Rahu and Ketu are a very dynamic and mysterious planet, their malefic/benefic nature is a function of a house, sign, and nakshatra they occupy.
This content was originally published on Quora by the author of this blog
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