Constellations have always been a mystery to humans, are they representations of god? Do they affect us in any kind? Why are they even there?

Let’s answer some of the most asked scientific questions in astronomy, related to constellations.

Constellations are groups of stars in the night sky that can form an outline, pattern, or particular shape to which human beings assign significance. This might be simply a name to remember them by, or it might be how our ancestors determined the time of year.

A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.

Let’s answer some of the most pressing questions on constellations

Q1. Why did people start making patterns in the sky?

Since prehistoric times, humans have been using the stars to help them navigate their surroundings, whether it was just down the path from their cover, for seasonal migrations, or even across the ocean to reach new grounds. But they didn’t just use individual stars, they used constellations, the most important guiding lights in the night sky.

Typically, these patterns depict animals, religious or mythological figures, or an inanimate object, perhaps with personal cultural significance. 

Constellations themselves are not uniformly defined across cultural groups, and since the positions of stars vary over time, the figure of constellations do as well, so the constellations that our ancient ancestors saw in the night sky were likely distinct in appearance from the ones we know today.

In Ancient times, constellations were used to develop and track the calendar so they knew when to plant crops and harvest them.

Q2. What is the most historically significant incident that happened because of constellations?

We’ve always had a fascination with the stars, bright beacons of light that come alive when the sky blackens. They’ve been revered as gods, used to mark changes in the seasons, and as a way to navigate the world. It’s difficult to trace back when exactly people began looking up and taking note of familiar patterns that were formed by these points of light, but some propose that 17,000-year-old cave paintings in Lascaux, France, depict the constellations we today know as Taurus and Orion.

Although there are older records from many different places and cultures that tell their own stories, it is the ancient Greeks that made a lasting impact on astronomy. Claudius Ptolemy, a Greek astronomer who lived in the city of Alexandria in the 2nd century A.D., made a comprehensive list of 1,022 stars, illustrating them as members of 48 constellations, many of which adopted imagery from Greek myths and legends and older Babylonian ideas. This ancient text, called Almagest, became the basis of what we recognize in the sky today.

Mayans were keen astronomers, tracking the sun, moon, planets, and Milky Way across the heavens, and constructing incredibly accurate calendars for the time using their knowledge. They built many structures and buildings to align with certain stars, and there’s evidence they had a 13-star Zodiac that took the shapes of native wildlife. Polaris was also known to the Maya, though they knew it as Xaman Ek. It was sometimes associated with the rain god who brought the storms of winter.

Q3. Why are constellations still in use?

The first use for Constellations was probably religious. People thought that the Gods lived in the heavens and that they created them. Many cultures believed that the positions of the stars were their God’s way of conveying stories. So it seemed natural to recognize patterns in the sky, give them names, and tell stories about them. We inherited the names for our constellations from the Greeks. And they named the constellations after their mythological heroes and legends. So behind every constellation, there is a story. For example, to the ancient Greeks, Orion was a great hunter. He was the son of Neptune (god of the sea). But the same stars were considered to depict Osiris by the Egyptians. Each different culture developed its own interpretation.

The constellations have a practical purpose today too. They determine how stars are named. When astronomers go to conferences they like to share their research with others. And usually, they will want to tell someone which stars or objects they may be looking at. If they just give the coordinates (numbers) the other person is not likely to have an immediate idea of where the star is located in the sky. But if you say that the star’s name is Alpha Tau then you will know that is the brightest star in the Taurus constellation. The stars are named based on the constellation they are in (all stars are in some constellation). The naming goes from brightest to dimmest star and is designated by the Greek alphabet. For example, Beta Ori is the second brightest star in Orion (also called Rigel).

Q4. Which are the internationally recognized constellations?

Currently, there are 88 formally recognized constellations established in 1922 by the International Astronomical Union.

They are:-

While the importance of any constellation is highly dependent on what you might need it for (i.e., navigation), there are about a dozen major constellations that appear along the ecliptic of the solar system, an imaginary line along the perceived path of the sun (as well as the rough paths of the planets and the moon) over the course of a year on Earth. 

These constellations are low enough on the horizon that the planets, the Moon, and the Sun all appear to move “through” them, and so these constellations, known as the western zodiac, have taken on special significance.

These are-

• Aries
• Taurus
• Gemini
• Cancer
• Leo
• Virgo
• Libra
• Scorpio
• Sagittarius
• Capricorn
• Aquarius
• Pisces

Q5. Will constellations be there forever?

The quick answer is no, they do change over time. Far from being the fixed points of light as believed by the ancients, the stars we see, along with the Sun, are in constant motion, each along its own orbital trajectory around the centre of mass of our Milky Way Galaxy. They all pretty much circle in the same direction as they revolve in their wide, lengthy galactic orbits, but each star’s path is its own, like the orbits of the planets around the Sun. Each star’s orbit may be inclined (tilted) with respect to others, and their velocities rely in large part on their distance from the Milky Way centre. 

Well, for example, the star with the fastest proper motion in our skies (at this time) is Barnard’s Star, a small, low-mass red dwarf about 6 light-years away in the constellation Ophiuchus, the Snake-holder, just above Scorpio. It’s occasionally called “Barnard’s Runaway Star” because of its high velocity, a tiny stellar bullet whizzing through our neighbourhood on its way to whatever destiny. To give a feel of its physical speed, its radial velocity is about 110 kilometres per second away from us. And the proper motion of Barnard’s Star is (drumroll please): 10.3 arcseconds per year. That’s 10,300 milli-arcseconds per year—darned fast considering all but the nearest stars move at most by a few up to a few hundred milli-arcseconds per year.

So the other part of the answer—how long does it take for a stellar proper motion to change the patterns we see in the constellations—is: pretty long, especially considering that Barnard’s Star (Add to this the fact that Barnard’s Star is too faint for the human eye to perceive, anyway!) With even the brightest stars showing less proper motion than Barnard’s Star, it’s easy to imagine why those ancients saw pretty much the same constellations we see today. Imagine also that a thousand years from now, our distant descendants will regard the same patterns.