Oct 5, 2021
Introduction to our familiar stars in Vedic Astronomy
To understand the concept of star identified for a particular day, let us see the concept of how moon gets involved in the process.
Synodic vs. Sidereal Month
The time it takes the Moon to complete one orbit around Earth is called a sidereal month. Sidereal refers to the Latin word for stars and sidereal month means that the Moon returns to the same point under the stars. This takes, on average, 27.3 days.
If Earth stood still, the synodic (lunar) month would be the same as the sidereal month. However, at the same time as the Moon is orbiting Earth, our planet also continues its annual orbit around the Sun in the same direction. So, after completing a sidereal month, the Moon has to move a little further to catch up to the same alignment with the Sun and Earth as at the previous New Moon. This is why a synodic (lunar) month is around 2.2 days longer than a sidereal month.
The moon is concerned only with months and then it is only the sun that is concerned with years. So the month is concerned with the moon’s orbit and the year is concerned with earth’s orbit.
The Chandramaana lunar calendar system keeps a natural cyclic count of days using two Moon based properties described below:
1)First property is that moon functions as an astronomical day count clock in which Moon is the pointer and the stars are numerals in the sky pointed to by moon each day of the lunar month. The astronomers of Vedic period identified this approximate 13 degree movement of the moon between successive days and named the 27 stars pointed to by moon on a daily basis over a rotation as 27 nakshatras, corresponding to little less than a lunar month. Thus a Nakshatra shift corresponds to moon traverse over approximately one solar day.
2)The second property is the size of fractional moon exposure to sun can indicate a day count and is defined as a moon day or thiti. Thirty thiti’s are defined in a lunar month, each thiti being smaller than a solar day. Fifteen are identified as Shukla paksha or ascending fortnight and next fifteen are called krishna paksha or descending fortnight.
This system of day count calendar keeping, is traceable to Veda’s. Pournamsya, a time at which earth, sun, moon are aligned is a time of singularity used for religious purposes and formed the unit of half a month and is used in Rigveda.
Now, for a given day, the star mansion/nakshathra is determined by the position of moon near it. If we dig up the reference to nakshatras in vedas, we end up with the recording of Gargya Rishi in Atharvana veda’s 19th kaanda/ 7th suktha.
Sooktha 7:A Prayer to the Lunar Mansions and other Powers for protection and prosperity
The brilliant lights shining in heaven together, which through the world glide on with rapid motion.
And Days, and Firmament with songs I worship, seeking the Twenty-eight-fold for its favour.
Krittikās, Rohinī be swift to hear me! Let Mrigasiras bless me,
help me Ārdrā!
Punarvasu and Sūnritā, fair Pushya, the Sun, Asleshās, Maghā
lead me onward!
My bliss be Svāti and benignant Chitrā, my right First Phalgunis and present Hasta.
Rādhas, Visākhas, gracious Anurādhā, Jyeshthā and happy-
starred uninjured Mūla.
Food shall be earlier Ashādhas grant me; let those that follow
bring me strength and vigour;
With virtuous merit Abhijit endow me! Sravana and Sravishthās
make me prosper.
Satabhishak afford me ample freedom, and both the Proshtha-padas guard me safely.
Revati and the Asvayujas bring me luck, and the Bharanis
abundant riches!
It is interesting to note that Rishi Gargya has captured the start of nakshatraas as Krithikai with that of equinox happening then during the vedic period and also marking the start of the year. However, in jyothisha shastra, much later, the equinox is marked along Ashwini nakshatra as the start of the year, giving a clear indication of the astronomical activity identified as Earth’s Precession.
Now that we have had an introduction to the mention of lunar mansions/ nakshatras in our Vedas, let us have a look at Ashwini nakshatra captured in the Mesha raasi/ Aries constellation with the help of astro-photography in our next story. Until then have a wonderful time! :-)
