E019 The Zodiac and 27 Nakshatras: An Astronomical Perspective – Part 3

Known is little!

Those 27 Nakshatras

If you haven’t read first and second parts of this series, please get started from there for a better understanding. In the first two parts of this series, we looked at the Universe, the 12 constellations on ecliptic path of Sun and the Rashi length comparisons between astrology texts and recent astronomical data. In this third part, we will get to know more about the 27 nakshatras / stars through astronomical data.

One of the fundamental and differentiating principles of Indian astrology is the use of 27 nakshatras or stars. While the 12 zodiacs are generally used in astrological systems across world, only in Indian astrology we can find more elaborate use of 27 nakshatras for readings and making predictions. The dasa-bhukthi calculations are based on the moon’s position over these 27 stars at the time of birth for a person.

Vedas identify these stars as abodes of different gods (Devas or Angels 😊). Majority of astrologers assign great importance to these stars on several aspects of astrological predictions (including marriage match making). There is a popular explanation given by some leading astrologers that moon receives the light from these stars and passes them on to us. Many followers of those astrologers also tend to believe in such statements, instead of questioning the astronomical merit behind.

Based on these 27 star positions, Ephemeris (Panchang) systems also get divided into Thirukanitham and Vakyam systems in Tamil Nadu. Followers of these two systems often clash in social media arguing about the superiority of one system over the other. Fortunately, this never-ending fight seems to be limited to the boundaries of Tamil Nadu. Astrologers from other states or countries do not seem to bother much about such differences.

In Indian astrological calculations, varying rashi lengths are defined. However, when it comes to casting Rashi charts, a standard 30°per rashi is used for calculations. The 360-degree of ecliptic path is equally divided between 12 zodiacs (30°each) and 27 stars (9°20’ each). Even a slight change in this degree numbers can potentially alter rashi or nakshatra pada, which ultimately will lead to differences in astrological readings and interpretations. If such star positions are so critical, then it becomes imperative to validate such star positions with astronomical data or evidence. This article is an attempt to validate astrological data related to stars with real astronomical data.

IMPORTANT NOTE: I have used this wikipedia page as my base to build upon. Most of the astronomical data used in this article have been sourced through Stellarium software. Enhanced data points from International Astronomical Union have also been used, wherever available.

Those 27 Nakshatras:

A star is a unique celestial entity which may or may not have some planets orbiting around it. For example, our sun is a star. In Indian astrology, though we refer to 27 stars, each of these star names in fact refer to a collection of Taras / stars (தாரை in Tamil).  Tara can refer to a single star, a group or collection of stars. These Taras can be part of the 12 zodiacs or other constellations. You can find references to number of stars against each of these 27 stars in few astrological texts. An enumeration of such Taras in fact yield a whooping count of 73 Taras against these 27 stars!

I have taken into account those Taras and have cross-validated with Stellarium asterisms data points with some fixes made to the counts from astrological texts. For example, Shatabhisha (Satayam in tamil; HIP 110395) nakshatra is stated to have 100 Taras. However, astronomical data indicates only one Tara against this star. These 100 Taras might have been assigned just to indicate greater astrological significance to this star.

Each Stars can be further classified into single (like our Sun), binary or more based on number of stars involved per Tara. A binary or double star would have two stars orbiting around each other with some common point. An analysis of data reveals that most individual Taras (54 out of 73) are in fact the binary or three stars. Only 19 out of 73 Taras are single stars, like our Sun.

Check out the image below for an enumeration of such Taras per Nakshatra.

Taras per Nakshatra
Taras per Nakshatra

The number of individual Taras is shown behind each star. 1 * represents single Tara and 2 * represents two Taras and so on.

These Taras are shown in more detail in the following image. Depending on the Lord assigned to a Nakshatra, stars have been grouped in different colors. The star order number is given below the star name.

Taras by Star name
Taras by Star name
  • Mula (9) followed by Krittika (8) have maximum number of Taras.
  • Of the total 27 stars, only 8 have single Taras (Rohini, Ardra, Magha, Uttara Phalguni, Chitra, Svati, Shatabhisha and Revati. All of them belong to binary star system).
  • Another eight nakshatras have two Taras each.

The star asterism and image of individual stars are shown below for one of the popular and bright Nakshatra named Krittika.

Taras of Krittika
Taras of Krittika
Stars in Krittika
Stars in Krittika
Image courtesy: •By NASA, ESA and AURA/Caltech – Hubble Refines Distance to Pleiades Star Cluster (STScI-2004-20), Public Domain, https://commons.wikimedia.org/w/index.php?curid=17899258

Explanation for Nakshatra selection vs astronomy data

There is popular explanation given for inclusion of Nakshatra to this coveted 27 listing. It states that brightest stars that can be easily identified with naked eye in a constellation have been chosen as one of these 27 markers. However, astronomical data does not appear to support that popular view.

See the Aries asterism image below to understand more about this statement. The image shows the taras of Asvini and Bharani nakshatras along with another bright star.

Mesha Rashi

Alpha Arieties (popular name: Hamal), is the brightest star in this constellation. However, it has not been included in Indian system, though used in other systems. For your information: In one system of star names, they are ordered based on their brightness starting with alpha as the brightest star.

Color spectrum of stars:

Depending on the nuclear activity and fuel levels in stars, they emit light at different wavelengths ranging from blue to red. The blue ones are fuel-rich stars that have massive nuclear reaction. Stars that exhausted their fuel will show up in red colour. Stars that lie in middle range typically emit light in yellow band (just like our sun). Based on this information, look at the image below. One of the brightest stars in constellation of Leo is the Magha nakshatra (shown in blue). In its vicinity (two-dimensional), you can see other stars that emit different colors.

Magha Nakshatra
Magha Nakshatra

In the next image below, some of the stars in the constellation of Aries, their astronomical identification, and colors they emit are shown. This asterism is of western type. You can observe some small differences in shape between this asterism vs its Indian version.

Nakshatras of Mesha / Aries
Nakshatras of Mesha / Aries

Even though the stars we see in a zodiac appear to be nearer to each other on a flat 2-D view, when viewed in three-dimensional space, they lie at distances far apart. This distance can extend to several hundred light years. We will have a detailed analysis on this aspect in a later chapter. In the image below, a side view of Aries constellation you have seen above is shown, which provides a rough idea of the distance between different stars.

Aries - 3D View
Aries – 3D View – Side View

My base data catalogue:

I have collated following information on 27 Nakshatras, their Taras, the order in which they are placed on the ecliptic grid and their Rashi lords. As mentioned in my previous article, I have used Hippacros (HIP) codes as primary identifier. I am also providing their IAU designation and IAU names for your reference in the tables below. This baseline data will serve as reference data set for my analyses.

Ketu – Venus – and the stars of the sun

Though 3 nakshatras each are assigned to a planet, the underlying Taras vary greatly. In the table above, you can see that Ketu has 12 Taras in total, referred as Ketu (12).

I have also provided their star type (single, binary or more) for your reference. For example, HIP 8832 A is a binary star and HIP 82396 is a single star. Likewise, you can understand others.

Ketu (12) and Sun (11) have maximum taras assigned to them.

Moon – Mars – Rahu stars

Interestingly, Rahu’s all nakshatras are of single taras. Rahu’s stars are relatively brighter and widely referenced in other worldly systems as well.

Stars of Jupiter – Saturn and Mercury:

  • Except for Revati nakshatra, all stars of Guru, Saturn and Mercury have more than one tara per nakshatra.
  • All nakshatras of the Sun, Saturn and Rahu consists of stars having binary or more stars system.

Astronomical data on celestial location, brightness, distance from sun, proper and lateral motion, and rate of movement are interesting for these 27 nakshatras. They have the potential to challenge some of the popular beliefs and hear-says of many astrologers. We will delve into them in the successive chapters of this article series. Key astronomical data and their significance to astrological constructs will be revealed in the upcoming articles. After reading those articles, when you see those 27 stars next time in the night sky, you will see many more things than some twinkling stars. Be patient until then! 😊


Astronomy Software Courtesy: Stellarium, and Night Sky for iOS

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