Constellations And The Zodiac

Note: I was planning to write on Constellations as a separate thread when I write about stars.
However, as Ms.Jayasala had posted some query in the Jupiter thread I have decided to introduce constellations now.
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This is my response to queries raised by Srimathi @jayasala42 ma'am

Constellations - What are they?

Image courtesy: astronomytrek.com

Whenever we look at clouds sometimes we see images. We think there is a dog or a face or a tree.
Our brain likes to conjure patterns.

When our ancestors looked up at the millions of stars in the night sky they began connecting some stars with imaginary lines to create a picture or figure.

These group of stars that formed the pictures are called constellations. The pictures are all imaginary.

Constellations were very useful for our ancient travelers and before calendars were created farmers did not know when to sow and when to harvest. They depended entirely on the constellations. Constellations also were good reference points for astronomers.

Many cultures had different sets of patterns and different names for the same set of stars also. The first known record of a constellation dates to as early as 17,000 years ago.

A number of mythological stories and personal experiences also were centered on these constellations.

As more stars were being discovered and more constellations were being introduced, in 1922 the International Astronomical Union (IAU) decided to create an official set. Most of the original constellations (Ptolemy and other earlier European astronomers) were retained and some new ones were introduced.

In 1930 the entire sky visible from Earth (both Northern and Southern hemispheres) was divided into 88 regions to provide clear demarcations between each constellation.

Stars in a constellation

From Earth’s perspective stars in a constellation appear to be close to each other. That is because we lose the sense of depth when we view the night sky and we see only two dimensions.

The stars in any constellation are far from each other and different in sizes.

For example in the constellation Aries there are three major stars. Alpha, Beta, and Gamma Arietis. Alpha Arietis is 66 light years away from Earth while Beta Arietis is 59 light years away.

Astrology

Of the 88 constellations, thirteen constellations move along the ecliptic path of the Earth. In actuality it is the Earth that moves and it appears that the sun and stars are moving.

Of these thirteen, astrologers use twelve (omitting Ophiuchus) to make predictions. Astrology is not a science. In ancient times Astronomy and Astrology were sister sciences, developing side by side, at one point Astrology was more important.

Astrology ceases to be a science in modern times as it has been proved that the future predictions and personality analyses based on star/planetary position have no scientific validation.

It is interesting to know that a person’s zodiac sign is not the constellation that is visible at night. That’s because it was believed that sun stays in that particular zodiac that is associated with the birthday of a person.
For example if you were born March 27 your zodiac is Aries, in the night sky you will see the opposite constellation “Leo”.


Image courtesy: j-journey.com

Jupiter and the zodiac.

The planets always keep to their elliptical path. They do not swerve away from their orbits.

The term “occupying” a zodiac/constellation is really a misnomer (if that is the right word). It is actually an illusion that Jupiter is occupying a zodiac.

Jupiter is relatively closer to us that the stars.

As Jupiter orbits the sun, we, from Earth, see the different constellations along with it though they are in the background. The two-dimension effect makes it appear as if Jupiter occupies that particular constellation (zodiac in astrology)

Currently I believe Jupiter is “occupying” the constellation “Scorpio”.


Image courtesy: space.com

Though Jupiter is only about 5 AU away from the Earth these stars in the constellation Scorpio -

• Shaula is 587 light years away,
• Antares is 619.7 light years away and
• Dshubba is 443 light years away,

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they all appear on the same plane to us.

The period of stay is determined by the fact that Jupiter’s “path” or orbit is far away from the Sun and it takes 12 years for to complete one orbit. Therefore it appears to us as if Jupiter stays in one constellation, which is one year.

Similarly Saturn, which is farther away from the Sun, takes 29 years to orbit around the sun, taking about 2.4 years to move from one constellation zone to the next.

I drew this image to illustrate this. Not sure if you could see it clearly.



Please let me know if you have any more questions.
Thank you

 

Thank you @Rihana
While I knew what to say, the challenge here was how to say it, so the reader can visualize the heavens easily. I took the whole of Saturday searching for a good picture and finding none, finally decided to draw it myself. First was a free hand sketch, which was full of scratched lines and worst of all, my handwriting So opted for the digital version.

 

Thank you @GeetaKashyap .

 

Thank you @periamma . Glad you liked it.