E017 The Zodiac and 27 Nakshatras: An Astronomical Perspective – Part 1


Our ancient astrologers possessed sound astronomical knowledge. They were knowledgeable to identify key nakshatras, planets and their positions, Rasi that is arising on eastern horizon without the help of Ephemeris on any given day. Majority of current generation astrologers lack those observational and recognition skills and their knowledge of astronomy is mostly hear-say in nature. Without a strong footing on basic astronomy, the level of conviction in one’s astrological assessment and predictions would be shallow.

Astronomical accounts of the zodiac and nakshatras that are important to Indian astrologers are relatively old, scarce (especially in Tamil) and may not be easily available in public domain. Astronomers look at astrological zodiacs and stars differently than astrologers and did not bother to build the connection between those two. Many Astrologers lack astronomy domain knowledge and tools to make those connections themselves.

Lack of tools to help visualize astronomical concepts, professional restraint to question existing realm of ancestors’ knowledge, unquestionable faith in the existing traditional knowledge assets and fear of being rejected by fellow community members could be the reasons for many astrologers not trying to validate the astronomical concepts that have been told to them over generations. Over time, this has severely deprived an astrologer from learning the strong astronomical fundamentals behind astrological constructs. This article is an attempt to bridge that gap to some extent. I hope this essay will provide a sound base to friends who are learning astrology and to those souls, who question astronomy behind astrology.

IMPORTANT DISCLAIMER: I am no expert in astronomy and have written this article with my limited understanding of the subject. This being an article to fill some knowledge gap for a specific community, those with professional expertise in astronomy should feel welcome to help improve this content. The astrologer community will feel obliged to you if you do so.

In this article, let us take an astronomical view of the zodiac system, which is common to astronomy and astrology. In subsequent articles, I will write in depth about some verifiable characteristics of constellations including their length, position of Nakshatras we use in Indian astrology etc. This article is an attempt to investigate / confirm to what extent the astronomical assumptions provided to us in astrology texts are closer to reality. Hence, this article may differ from the astronomical data you would have acquired in astrology books.

The readers are requested to approach this article with an open mind, free from prejudice. This article is not an attempt to downplay any astrological constructs or methods of our ancestors. Rather, this is an honest attempt to showcase the strong astronomy knowledge behind the mathematical modeling framework used in astrology and the great observational skills of our ancestors. I hope that this essay will be a milestone in my pursuit to bring out connections between astronomy and astrological constructs.

Since the nature of this topic is so deep and lengthy, I will only briefly touch upon key astronomical concepts. Readers interested to get more deeper knowledge are requested to pursue their studies further.

The Universe – A quick introduction

Have you ever had the experience of witnessing numerous stars and our solar system planets in the sky, lying on the terrace of your home on clear nights? Have you tried watching those objects with telescopes or binoculars? Have you looked at the beauty of moon through lens? If you have not done any of this, please make it a point to do them soon. Even though we cannot see our Creator in person, we can realize his enormity and infiniteness of him through the night sky.

Star gazing is as entertaining as watching a happy elephant or its playful calf. No matter how long, how far and how wide we see, all we get to see before our eyes is only a miniscule of the giant cosmos. Our universe is not alone. Today, Science is talking about the existence of multiverse. This has been elicited in the Bhakthi literature of Tamils several hundred years ago. For example, ancient tamil literature Thiruvasagam by Manikavasagar has set of verses (Chapter 3 – Thiru Andapaguthi) describing about the multiverses and the infiniteness of the creator. 

Our Universe consists of billions of galaxies, including our Milky way galaxy. In the picture below, our Milky Way galaxy and its different arms are shown. Our Sun is placed in Orion spur of the Sagittarius arm.

The Milkyway Galaxy

Milky Way Galaxy – Some notes:

  • According to current scientific understanding, our universe was formed by a ‘Big-Bang’ that occurred 13.77 billion years ago.
  • The first stars appeared 400 million years later.
  • Our Milky Way galaxy, which was formed after them is 13.6 billion years old.
  • The Milky Way galaxy has a plate-like structure that is bulged in the center, with the old stars at its periphery.
  • The Milky Way galaxy is like a rotating fan with 4 circular arms. In each arm, several thousand billion small and large sized star clusters are moving at different speeds.
  • Our universe is expanding continuously. In this expanding universe, all objects are moving away from each other. For us, stars near us are moving away from us at a slower rate than stars that are far away from us, which are moving away at a higher velocity.
  • It takes about 250 million years for the sun to orbit our galaxy. Our Sun has already completed 20 such revolutions since its birth. At times, it has been in and out of the rotating arms many times. These rotating arms serve as nurseries for birth of new stars.
  • At the center of the universe’s spiral is a giant black hole that is gulping everything on its path. Science has discovered that small sized black holes are omnipresent across the entire universe.

If we zoom-in to the above image, it will look like the one below.

Expanded view

These pictures may give you a sense of how miniscule our solar system is compared to our universe. As far as science is concerned, life exists only on this earth. Indian devotional Bhakthi literatures like the one I cited earlier, however assure that several such abodes exist. Let us pray that our modern science finds those abodes soon! 😊

Like in Indian mythological story where Brahma and Vishnu sought to find the beginning and end of the infinite Lord Shiva, today, science continues its search for the beginning and the end of ever-expanding cosmic space. 😊

Astronomical Science and the art of Astrology

Realizing that we are a miniscule of the universe itself and neighboring objects in it will have some influence on any celestial object, some wise men (sages) resorted their quest inward. The saints saw our existence and lives as principles that can help us lead a meaningful life, which are further varying with the combination of different qualities and characteristics. They were able to attribute these characteristics to planets from Sun to Saturn with some overlapping features. They devised way and means to represent human life and events through these combination and placement of planets in birth and transit periods, refined that knowledge through detailed observations of planets and life events of people over period of centuries and catalogued that wisdom as principles of astrology.

* Note: In my opinion, the reason why we consider only from sun to Saturn in Indian astrology can be justified through mathematics / statistics as well. I am reserving that interesting discussion to a later date.

The Star Space

We can see up to 6000 stars with our bare eyes from entire earth, which greatly vary in size and brightness. Based on earth’s tilt, geographic location and culture of the land, these distant bright objects would have appeared as interesting shapes that people could make up, which were related to objects and beliefs in their daily lives. This conceived view of fixed stars as different shapes in space was necessary for them to identify and measure the location of moving Grahas over this star street. The Rasi (collection of nakshatras) / nakshatra backdrop perfectly served as a fixed background screen to track the moving planets.

Though there are few thousand stars on the stellar space, stars near the ecliptic orbit of sun was considered more important from an astrological perspective as all the planets under astrological construct closely tracked the same path from a two-dimensional perspective. When simulating a mathematical construct, using astronomy, it became necessary to divide this large orbit of sun into smaller distances of manageable size to represent smaller units of time (as it takes one year for sun to complete this orbit from a geo-centric perspective). The stars along and near this ecliptic path were used as markers and hence assumed greater astrological significance. To easily identify mathematical boundaries, such star markers were assumed to be part of different shapes/objects found in nature, which we call as constellations. These hypothetical two-dimensional fusions of the stars considered to determine the boundaries of the ecliptic path are the 12 constellations we use in astrology. This astronomy knowledge should have evolved on one part of the earth. With migration of human beings and trade between them later, such knowledge of constellations should have been exchanged, refined, and altered locally to suit the location, culture and different times.  

Since stars are represented by different names and different constellations across nations, a need to catalogue them with boundaries was realized in last century. Beyond zodiac that covers the 12 constellations, western astronomers have defined 88 zodiacs and their boundaries considering the entire area of Earth’s outer space.

Check out for such an image below.

Modern Constellations with Boundaries

This picture is a representation of such constellations with their boundaries, which came into effect after the 1930s. Keep in mind that the zodiac boundaries and asterisms used in most mobile applications are primarily western and not based on Indian astrology. I have not personally come across any literature that clearly define the boundaries between 12 constellations beyond their probable asterisms.


As part of a precise astronomy catalogue of stars, it became imperative to clearly identify the celestial coordinates and other properties of stars such as their brightness, size, distance, proper motion, parallax movement and speed and angle of motion. Towards this objective, a mission named Hipparcos was taken up in 1989 (Hipparcos – https://www.cosmos.esa.int/web/hipparcos/home ) by the European Space Agency. This satellite was in operation till 1993 and provided accurate astronomical data for 118,218 stars. Its outcome was released in 1997 as a catalog. This was followed by the launch of a space observatory name Gaia (https://www.cosmos.esa.int/web/gaia ) in 2013 and is currently in operation. This mission is expected to provide an extraordinarily accurate three-dimensional map of 1 billion stars in our galaxy and beyond. Please note that data used in my articles are based on Hipparcos catalogue.

Determination of location and distance of the zodiac constellations or stars:

Zodiac constellation are a collection of specific stars. The location of stars can be represented as a coordinate of two points (latitude and longitude for equatorial grid; right ascension and declination for the Celestial Sphere) based on imaginary lines drawn on celestial space.

Images below are based on ecliptic grid. Since our Earth is tilted to 23.5 degrees on its axis, if you look at this from the Earth, Sun’s ecliptic orbit would look like a curve passing on both sides of equator line instead of a straight line.

Below are the images of the zodiacs that our ancestors of various regions considered in their time. These images of constellations were derived from Stellarium astronomy software. Such rendering and visualization were not available to our ancestors.

  1. Zodiac set of Arabs
  1. The zodiacs of the Babylonians

3. Zodiac of the Egyptians


4. Chinese Zodiac

  1. Zodiac metaphors of the Mayans
The Mayans
  1. Western zodiac asterisms
Western Zodiac

The zodiac considered in our Indian astrology would look like the picture below. Assume that you are viewing this picture from top of the solar system.

Indian Zodiac

In the picture above, geocentric view is provided. You could observe the earth’s precession circle of north pole marked for our reference with our current pole star identified.

If you expand the image into a rectangular view, it will appear like the image below.

Indian Zodiac on Ecliptic Grid

In the picture above, the orbits of the planets along Sun’s ecliptic path are shown by differently colored lines.

  • You can observe that different Rasis have different lengths (horizontal distance).
  • You can also observe the gaps between few constellations of zodiac.
  • Some of the constellations overlap sharing common space (For example:  Capricorn and Aquarius).
  • Most interestingly, you can also notice that some of the stars we consider in Indian astrology lie outside the boundaries of 12 constellations of zodiac.

Let me end this first part here. We will discuss about the above said observations in detail in my upcoming articles. In the next article, I will analyze lengths of Rasis through astronomical data and compare them with what is available in standard astrology texts.

Thanks for your time and interest so far!

Feel welcome to share your comments below.

Software Courtesy: Stellarium 

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