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Wikipedia / Nakshatra

Nakshatra () is the term for a lunar mansion in Hindu astrology and Buddhist astrology. A nakshatra is one of the 27 (sometimes 28) sectors along the ecliptic. Their names are related to the prominent star or asterism in or near the respective sectors. Every nakshatra is divided into four padas ( "steps").

The starting point for the nakshatras according to the Vedas is "Krittika" (it has been argued that this is because the Pleiades may have marked the start of the year at the time the Vedas were compiled, presumably at the vernal equinox), but in more recent compilations, the start of the nakshatra list is the point on the ecliptic directly opposite the star Spica, called Chitrā in Sanskrit. This corresponds to Ashwinī, a part of the modern constellation of Aries. These compilations, therefore, may have been compiled during the centuries when the sun was passing through Aries at the time of the vernal equinox. This version may have been called Meshādi or the "start of Aries".

The first astronomical text that lists them is the Vedanga Jyotisha.

In classical Hindu scriptures (Mahabharata, Harivamsa), the creation of the asterisms is attributed to Daksha. The nakshatras are personified as daughters of Daksha and as wives of Chandra, the god of the Moon. When Chandra neglected his other 26 wives in favour of Rohini, his father-in-law cursed him with leprosy and proclaimed that the Moon would wax and wane each month. The nakshatras are also described as the daughters of Kashyapa.

Nakshatra is one of the five elements of a Pañcāṅga. The other four elements are:

Etymology

The sanskrit term naksatra denotes a special class of heavenly bodies associated with the moon. The term naksatra consists of the root náks-(meaning "to attain") combined with the suffix -tra (or -l-atra, meaning "place"), meaning "the place to which the moon attains".

History

Historically, nakshatra referred to stars or star-groups associated with the Moon's path. In later jyotisha, the term also came to denote 27 equal divisions of the ecliptic. In this equal division system, each nakshatra spans 13° 20'.

In the Atharvaveda

In the Atharvaveda (Shaunakiya recension, hymn19.7) a list of 27stars or asterisms is given, many of them corresponding to the later nakshatras: Sakamoto-Goto identifies it as a hymn used for the daily worship of the nakshatras. The text lists 28 nakshatras, beginning with the Krttikās and including intercalary asterism Abhijit.

This 27-day cycle has been taken to mean a particular group of stars. This has to do with the periodicity with which the Moon travels past the specific star fields called nakshatras. Hence, the stars are more like numbers on a clock, through which the hands of time (the moon) pass. This concept is described by J. Mercay (2012) in connection with Surya Siddhanta.

Astronomical derivation of nakshatras

The choice between 27 or 28 nakshatras comes down to how ancient calendars calculated the speed of the Moon. During the Bronze Age (around 2000 BCE), astronomers used a calendar of 360 days, where the sun moved 1 degree per day and the moon moved an average of 13 degrees per day. Dividing the 360-degree sky by the Moon's 13 degree daily path gives an orbital period of 27.69 days .The astronomers rounded it to 28 nakshatras. Later, when a 365 day solar calendar was adopted, the Moon's updated daily speed of 13.2 degrees resulted in a shorter orbit of 27.27 days. Astronomers then rounded this down to 27 nakshatras and dropped the star Abhijit.

Vedic Calendar

The Vedic calendar was based on a 360-day solar year composed of twelve 30- day months. Its earliest mention is found in the Rigveda texts. It arose from a ritual need to identify the exact nights of the new moon (amāvāsyā) and full moon (puranmāsī) for sacred sacrifices, which were otherwise difficult to determine by naked eye observation.

The priests tracked the Moon's night-by-night movement against the fixed stars, establishing a system of 28 nakshatras(lunar stations) representing the 28 nights the moon was visible during a synodic month. Early astronomers derived the name of each month directly from the specific nakshatra in which the full moon shone during that month.

Vedic origin of tithi

The tithi is a lunar day in the Hindu calendar. In the 360-day vedic calendar, the Moon travelled an average of 13 degrees per day, while the Sun travelled 1 degree per day. As a result, the Moon separated from the Sun by 12 degrees (13 minus 1) every 24 hours. This time that the moon takes to pull 12 degrees ahead of the Sun, is called a tithi.

List of Nakshatras

In Hindu astronomy, there was an older tradition of 28nakshatras which were used as celestial markers. When these were mapped into equal divisions of the ecliptic, a division of 27portions was adopted since that resulted in a clearer definition of each segment, subtending 13° 20′ rather than the 12°′ that 28segments would give. In the process, the nakshatra Abhijit was left out without a portion. However, the Abhijit nakshatra becomes important when deciding on the timing of an auspicious event. The Surya Siddhantha concisely specifies the coordinates of the 27 nakshatras.

It is noted above that with the older tradition of 28nakshatras each equal segment would subtend 12.85degrees or 12°51′. But the 28nakshatra were chosen at a time when the Vedic month was recognised as having exactly 30days. In India and China the original 28lunar mansions were not equal. Weixing Nui provides a list of the extent of the original 28nakshatras expressed in Muhurtas (with one Muhurta = 48minutes of arc). Hindu texts note there were 16nakshatras of 30Muhurtas, 6 of 45Muhurtas, 5 of 15Muhurtas and one of 6Muhurtas.

The 28mansions of the 360° lunar zodiac total 831Muhurtas or 27.7days. This is sometimes described as an inaccurate estimate of our modern sidereal period of 27.3days, but using the ancient Indian calendar with Vedic months of 30days and a daily movement of the Moon of 13degrees, this early designation of a sidereal month of 831Muhurtas or 27.7days is very precise. Later some Indian savants dropped the nakshatra named Abhijit to reduce the number of divisions to 27, but the Chinese retained all of their original 28lunar mansions. These were grouped into four equal quarters which would have been fundamentally disrupted if it had been decided to reduce the number of divisions to 27.

Irrespective of why early Indian astronomers followed a Vedic calendar of exactly 12months of 30days it was this calendar and not a modern calendar of 365days that they used for the astronomical calculations for the number of days taken for the Moon to complete one sidereal cycle of 360°. This is why initially they named 28nakshatras on their lunar zodiac.

The following list of nakshatras gives the corresponding regions of sky, as per Basham (1954).

Padas (quarters)

Each of the 27nakshatras covers 13°20’ of the ecliptic. Each nakshatra is also divided into quarters or padas of 3°20’, and the table below lists the syllables traditionally used as the first sound of the name given to a child born under each pada. The 27nakshatras, each with 4padas, give 108, which is the number of beads in a japa mala, representing all the elements (ansh) of Vishnu:

See also

Notes

References