YOGATAARAS, THEIR MISIDENTIFICATIONS AND CORRECTIVE MEASURES M. A. Venkatachar* _____________________________________________________________________ Abstract Indian Astronomy is geocentric observational Astronomy. The stationary terrestrial observer is supposed to be at the centre of the star studded celestial sphere. The non varying great circle on the surface of the celestial sphere, representing the apparent annual path of the sun is the Ecliptic. The belt like region on the celestial sphere with the ecliptic as the central line and extending on either side of it by an angular width about 8 degrees is the Zodiac. In the all India Nirayana Luni-solar system of astronomy, starting from a special fixed initial point (origin) on the ecliptic, the ecliptic is divided into twenty seven (27) equal parts. Passing through the poles of the ecliptic, great semi-circles are drawn on the surface of the celestial sphere through these 27 points of section of the ecliptic. These great semi circles not only divide the entire surface of the celestial sphere into 27 equally spaced “Nakshatra Zones” but also divide the zodiac into 27 equally spaced regions called “Nakshatra Mansions” or Lunar Mansions. These mansions have been given Sanskrit names by ancient Indian astronomers. In each nakshatra zone, a visibly bright, conspicuous well known star (Nakshtra) is specially chosen and designated “Yogataara” (principal presiding star) of the nakshatra mansion. Thus, there are 27 yogataaras assigned to the corresponding 27 nakshatra mansions. The present paper analyses all aspects of the yogataaras, their definition, position, names, misidentification and proposed corrective measures in detail. Key words : Ecliptic, Zodiac, Nakshatra, Nakshatra Zone, Nakshatra mansion, Yogataara, Vernal equinox, Celestial Coordinates, Sayana and Nirayana systems. _____________________________________________________________________ *Retired Professor of Physics and Principal, Vijaya College, Bangalore – 560 004. Res.: #9, Mahantha Layout, Kempegowdanagar, Bangalore – 560 019. Tel.: 080-26620593. 26/06/2014 2 1. General Introduction The celestial sphere with its fixed stars, is found to rotate about its axis in space. For the geocentric stationary observer situated at the centre of the celestial sphere, independent of their distances from the terrestrial observer, the stars, planets (Grahaas) and similar bright objects appear to be on the inner surface of the celestial sphere along their line of sight. The Sun, Moon and other visible grahaas also appear to be moving with respect to the fixed star background of the rotating celestial sphere. Two important great circles can be imagined on the surface of the celestial sphere. They are (i) The Celestial Equator and ii ) The Ecliptic.1 The Celestial equator is the great circle on the celestial sphere whose plane is normal to the axis of rotation of the celestial sphere. The ecliptic is the unvarying fixed great circle representing the apparent annual path traced by the centre of the Sun on the celestial sphere. As these two circles are inclined at an angle called obliquity of the ecliptic, they intersect at two points called Equinoxes. The particular equinox through which the Sun 26/06/2014 3 crosses the equator from south to north is called the Vernal Equinox or spring Equinox and is given the symbol ‘ γ ’ (Gamma). To study the motion and position of the Sun and other planets (grahaas), two systems in use are popular. In the Sayana equatorial system ‘γ’ is chosen as the origin of the frame of reference. In the Indian Nirayana Luni-solar Ecliptic system the origin chosen by the earlier nirayana astronomers is a fixed point on the ecliptic diametrically opposite to the position of the very bright star spica (chitta nakshatra), the only bright star that is almost on the ecliptic. As per M.N. Saha’s Calendar Reforms Committees report2 of 1955 AD, this fixed nirayana origin of its frame of reference was also the position of the Vernal Equinoctial point during the year 285 AD. The members of the Committee, by back calculation have also found that at 21 hour, 27 minute (IST) on Sunday, the 22nd March of 285 AD, the Sun, in its journey on the ecliptic just crossed the Vernal equinox ( γ ). They, thus confirmed that it was the same point on the ecliptic fixed with reference to the star, ‘Spica’. This fixed initial point of the nirayana system is also called “The Nirayana Mesha Raasi Arambha Bindu” as also “The Ashwini Nakshtra Mansion’s Arambha Bindu” (starting point). While this point remains fixed with respect to the fixed star background on the celestial sphere, the position of the vernal equinox γ goes on sliding backwards on the ecliptic (Retrograde motion relative to the direction of the motion of the Sun) slowly as 26/06/2014 4 time progresses, due to the natural phenomenon called ‘Precession of equinoxes”. The angular distance of separation between the Sayana origin, γ and the fixed nirayana origin is called “Ayanamsa”. In fact, Ayanamsa which was zero in the year 285 AD has now increased to about 24 degrees in the year 2000 AD. It is this Luni-solar Nirayana System3 which is followed strictly in almost all regions of India. The speciality of this system is its concept of Nakshatra, nirayana raasi, tithi, yoga, karana, lagna, etc., which are not conceived in the Sayana system, though it has the varying tropical “Sun Sign” (raasi) concept. ‘Sayana System” is popular in many western countries. 2. Nakshatra, Nakshtra Zone, Nakshatra Mansion Nakshatra, Star, Taara, are synonyms representing self luminous celestial objects which appear as bright points on the celestial sphere independent of their size and historic. Many of them appear to be fixed over several thousands of years. Some of the them appear to be very bright and some others appear faint. Their apparent brightness is usually expressed in terms of numbers called “apparent visual magnitude”(M). Only nakshatras, whose apparent visual magnitudes are less than four (+4) are visible to the normal unaided eyes of human beings. There are about 600 nakshatras that are visible. Many of them have been assigned Greek, Latin, English etc names4 by astronomers. Indian, Sanskrit names are available only for a small number of visible bright starts. For example, the 26/06/2014 5 visibly brightest nakshtra “Sirius” (M=-1.47) is called “Lubtaka”; next bright nakshatra “Canopus” (M=-0.72) is called “Agastya”, Spica, M=+0.98 is called “Chitta” etc., Though more than 50,000 stars have been detected using powerful telescopes (with M ≤+8) and listed , Indian catalogues contain about 600 nakshatras (with M<+4), many of them without equivalent Indian names. Just as celestial equator and ecliptic are important great circles on the celestial sphere, there is another region enveloping the celestial sphere called the “Zodiac”1. This is a belt like region on the surface of the celestial sphere, with the ecliptic as its central line and extending on both sides of it at angular distance of about 8 degrees. This 16 degree wide Zodiac has special significance. While the Sun is moving on the ecliptic within the Zodiac all other visible grahaas (planets) known to ancient Indian astronomers are found to have their entire journey confined to this region only. In the Indian Luni-solar nirayana system, starting from its fixed origin of the ecliptic and proceeding in the direction of apparent motion of the Sun, Indian astronomers have divided the ecliptic into twenty seven (27) equal parts. Each part has an angular width of 3600 / 27 = 130-20’. The distance of any point on the ecliptic from the fixed origin is called the nirayana Celestial longitude (λN) of the point. As such, first part of the ecliptic has the nirayana longitude limit 00 to 130-20’. The nirayana longitude of the 26/06/2014 6 0 0 th second part extends from 13 -20’ to 26 -40’ and similarly the 27 last part has the 0 0 corresponding limits of λN from 346 -40’ to 360 -00’. The normal to the plane of the ecliptic, through its centre cuts the celestial sphere at two diametrically opposite points called “Poles of the ecliptic”. Passing through these poles of the ecliptic, 27 great semi-circles can be imagined to be drawn through the 27 points of section of ecliptic. The region between any two such consecutive (adjacent) semicircles is called “Nakshatra Zone”. Thus, these 27 nakshatra zones completely cover the surface of the celestial sphere and accommodate all the nakshatras and their constellations. These zones have a maximum width of 130-20’ at the ecliptic region. Further, these 27 semi circles will have divided the entire zodiac into 27 equal regions. Each one of these regions is called “Nakshatra Mansion,” also named as “Lunar Mansion” and forms the central part of the nakshatra zone. Starting from the fixed initial point on the ecliptic, and moving in the direction of Sun’s motion, the 27 nakshatra mansions have been named as (1) Ashwini (2) Bharani (3) Krithika (4) Rohini (5) Mrigashira (6) Ardra (7) Punarvasu (8) Pushya (9) Ashlesha (10) Makha (11) Poorvaphalguna or Pubba (12) Uttara Phalguna or Uttara (13) Hasta (14) Chitta (15) Swaati (16) Vishaka (17) Anuradha (18) Jyeshta (19) Moola (20) Poorvashada (21) Uttarashada (22) Sravana (23) Dhanista (24) Shatabhisha (25) Poorvabhadra (26) Uttarabhadra and (27) Revathi in this order. All the above points are more clearly illustrated in Figure-I. 26/06/2014 Ashwini Zone Bharani Zone ---w E--- St Figure-I: Nakshatras (Yogataaras), Nakshatra Zones, Nakshatra Mansions. P and P' - Poles of equator. K and K' - Poles of ecliptic Y - Vernal Equinox 0 - The fixed initial point - Nirayana Origin. YO - Ayanamsa ACDB- Ashwini nakshatra mansion; Sa-Ashwini Yogataara CEFD - Bharani nakshatra mansion; Sb- Bharani Yogataara co- obliquity of the ecliptic figure- not to scale 26/06/2014 7 3.