Gazing at the night sky, you’re bound to see the many star formations called constellations.
Our human ancestors gave them names and stories, used them to navigate, and created myths around their creation.
But are we seeing what they saw millennia ago? Do constellations change over time?
The answer is yes, constellations change, but it’s nothing we can observe during our lifetimes. Stars are so far away that even when they move at extraordinary speeds, they’re only moving in increments of a degree from their perceived location from the Earth. That’s why constellations don’t look like they’re changing, even though they are.
So how do we map the location of constellations and stars to see if it’s changed? Read on to find out!
Do Constellations Change Over Time? (ANSWERED)
How Are Constellations Formed?
We, humans, are pattern-seeking beings.
We want to see images of familiar things and tend to impart these patterns on any formation around us.
Constellations aren’t physical entities; they’re merely what our imagination as humans made of the pictures formed by the stars in the sky.
The stars forming constellations usually aren’t connected in any way. In fact, most of them are hundreds of lightyears away from each other.
There are 88 officially recognized constellations, the brightest of which have been known to ancient Babylonian, Greek, and Roman cultures as they can be seen by the naked eye.
The “ancient” constellations were 48 and then became 50 after Argo was split into three.
The oldest of the ancient constellations, Taurus, has been known since the Early Bronze Age.
As for the 38 “modern” constellations, they were discovered with the advent of telescope technology and access to the southern hemisphere’s night sky in the 15th century C.E.
Together with the ancient constellations; they map out almost all of the sphere of sky surrounding the Earth.
Do Constellations Change Over Time? And Why Does This Happen?
Now that we know how constellations are a construct of the human mind, we know that the stars forming them are independent of each other.
Every star has a mass and velocity as it moves through space. Some of them are incredibly slow, and some of them are pretty fast.
This means that within one constellation, you can have a star that moves faster than another.
However, our perception of this movement will vary depending on how far the constellation is from us.
To explain this further, let’s introduce the concept of proper motion.
What is Proper Motion?
Proper motion is the change in a star’s angular position from the Earth, which is the element of star movement we can perceive.
If the star is moving laterally, it’s moving from side to side in space, changing its position from the Earth.
However, if the star is moving radially, it’s getting nearer to or further away from us.
In this type of motion, we won’t be able to tell it’s moving because its relative position to the Earth is still the same, and the light coming from it won’t shine brighter or dimmer instantaneously.
Proper motion is measured in degrees, arcminutes, and arcseconds.
We mainly use arcseconds because even the fastest star in the observable universe, Barnard’s Star, only has the proper motion of 10.3 arcseconds per year; other stars only move a fraction of that.
To put this into perspective, if you extend your arm, the width of your pinky finger is about one degree.
An arcsecond is 1/1000 of a degree, so with some number-crunching, you’ll realize it takes Barnard’s Star a whopping 350 years to move one pinky width across the sky.
We can observe Barnard’s Star and note how fast it is because it’s only six lightyears away.
Still, the vast distance it covers in a single year is nothing compared to the distance its light has to travel to get to us.
So, the subtle differences from where the light is emitted are lost on us.
Now, to apply the same formula to the other stars in the 88 constellations –some of which are much farther away from Earth than six lightyears, it’s clear why we don’t notice the changes in star position.
Is There a Way to View the Constellations as They Appeared in the Past?
Being curious about how the night’s sky might have looked in the past is no strange notion.
That’s why astronomers mapped the stars as they are at the moment in catalogs, which were updated every so often to record the changes in star positions.
Nowadays, and thanks to the advancement in astronomy instrumentation, the changes in the rate of movement and its direction are recorded in star catalogs.
They’re available to the public through mobile astronomy apps and computer software that simulates planetariums.
You can download these apps that have the advanced features of browsing through the sky as it appeared thousands of years ago.
Stellarium Mobile, Sky Safari 6, and Star Walk 2 all have the option to choose the year, month, and day you want to see the sky.
Download one of these apps and give yourself the opportunity to look at the sky that the ancient Romans and Babylonians gazed at!
Conclusion
The stars have always been a source of fascination to humans, who weaved their stories into myths that are depicted in their formations.
Our early ancestors saw the constellations we see and marveled at them, which begs the question: do constellations change over time?
The answer is yes because everything in space is dynamic, and nothing stays in its place, especially giant balls of burning gas.
However, we probably won’t be able to observe the motion of the stars that leads to constellations changing due to multiple factors.
Stars move at incredible speeds, but thanks to the distance their light has to cover to reach us, we can’t really tell.
The vastness of space, combined with our limited perception of their movement, means that we won’t notice a discernible change in constellations during our lifetimes.
You might also enjoy learning about:
- Mensa Constellation Facts
- Lynx Constellation Facts
- Libra Constellation Facts
- Kid-Friendly Constellation Stories
- Can You Grow Grass on Mars?
- Can You Breathe on Venus?
- Stellar Parallax (What Are They?)
- Facts About the Sun
- Do All Planets Rotate in the Same Direction?
- Can You Breathe on Saturn?
