If you are one of the millions of people who believe in their daily horoscope,  or even if your are casually curious about it you’d have been hit with this news couple of weeks ago. For some true believers, this news has been heartbreaking  to hear that the Sun was not even in the constellation that they thought their sign was when they were born. If you were wondering how this drastic change in the Sun signs came about,  read on.

You need to get familiar with a few technical terms, in order to navigate.  Now, first things first – Let’s see what a constellation is.  Simplifying the definition given in the Wikipedia, I can say  ” a constellation is a perceived pattern formed by prominent stars within apparent proximity to one another.”  It must have been the bright sky without today’s light pollution coupled with the good imagination of the people from ancient civilizations that gave rise to these constellations. Many of the constellations were named after different animals or characters from mythological stories. I suspect  some of them were defined by people who really had some extra time at hand as well , because only a few constellations resemble the figure they were meant to represent! Here is the constellation of Scorpius, where it is indeed easy to imagine  a celestial scorpion is shown below.

The Constellation of Scorpius – The bent tail almost comes to life!


The next important term that you need to understand is ecliptic.  The ecliptic is the apparent path taken by the Sun on the celestial sphere.  If this definition sounds like Greek or Latin, the diagram on the side should help! The celestial sphere is the imaginary sphere around us.  If you project the earth’s equator on to the celestial sphere, you get the celestial equator. Since the Earth’s axis is not perpendicular to the plane it revolves around the Sun, the path of the Sun on the celestial sphere is also  at an angle to the celestial equator. This path is called the ecliptic. But how to observe the path of the Sun among the stars since no stars are visible when the Sun is around? By observing the eastern sky just before sunrise, and the western sky just after sunset, it was possible for ancient civilizations to maps the path of the Sum among stars. The ancient civilizations who defined these constellations also observed that this path passed primarily through 12 constellations, which they called the Zodiac. Each of the constellation in the zodiac was assumed to occupy 30 degrees of longitude on the celestial sphere – the amount of distance covered by the Sun in the sky in one month’s time.  Since the Moon, and other planets also revolve around the Sun in almost the same plane as the Earth, they are also always seen in the vicinity of the zodiac for Earth based observers.

There are two points in the sky where the ecliptic intersects the celestial equator. These are the days when equinoxes occur. One is the vernal equinox at the beginning of spring (so called vernal equinox), and the other beginning of the fall (autumnal equinox).  About 1500 years ago, the spring equinox coincided with the beginning of the constellation of Aries, and the Sun was at this position around the 14th of April each year. Due to the phenomenon called precession, the vernal equinox is moving slowly on the ecliptic and now actually occurs around the 20th of March each year.  However, western astrology still considers the vernal equinox as the ‘First point of Aries’ even though, the constellation of Aries may be far from it.

Until 20th century, constellation borders stayed sort of amorphous.  In 1925, the International Astronomical Association defined constellation borders assigning specific boundaries between all the constellations in the sky, and dividing all the area of the sky into 88 constellations.  When this new sky map was created, the ecliptic actually passed though 13 constellations instead of 12.  The Sun actually moves through the constellation of Ophiuchus, between Scorpius and Sagittarius.

In the map here, you can see that the ecliptic passes through Ophiuchus before going to Sagittarius. But all this change happened about 85 years ago. But then why is it making big news now?

It is just that a fact that was known to astronomers and for others interested in the sky, was brought out as ‘news’ 🙂 ! On January 15th 2011, when millions of people heard for the first time that the Sun goes through a 13th constellation, and when the exact times of the year during which the Sun is actually in a constellation were listed out  by Minnesota Planetarium Society, hell broke lose for a lot of believers!

Now lets assess what is the impact of this on your life. There are two options for you. If you believe in western astrology, you can take the following stand to stop lot of heart ache –  “According to western astrology, zodiac was divided the ecliptic into 12 equal parts. The first point of Aries has long since been disassociated with the constellation of Aries. So although I understand that the Sun was not even in the constellation of Leo when I was born, I am ready to believe I’ll have qualities of a Leo, because, well – astrology says so”.  This is technically a correct argument. In summary, your sign did not change, based on the principles of astrology.

If you are a non-believer of astrology like I am, and don’t believe that the Sun or the Moon or any stars can predict your fortunes, then well and good! You don’t have to care a bit about any definition or redefinition of constellation boundaries. After reading this post, you can be happy about knowing one new fact about the sky, though  😉


Picture source : Normally I make it a point to give proper credit to pictures that I use in the blog posts. Unfortunately this time, I regret not saving that information, and not providing it in the post

p.s:  This is a slightly modified version of the speech I gave today at my Toastmasters club. This was a project from the Advanced TM Manual – Speaking to Inform.