Have you ever gazed out at the night sky and been fascinated by a bright band of stars that lights it up? That’s the Milky Way. And over there is the Mars Bar. The sky is full of candy bars.
Nope, just kidding!
Let’s know how old is the universe?
While the exact age of the universe has been debated by scientists since the early days of quantum theory, the debate has largely been resolved.
Astronomers have a good idea of the age of the universe based on the light of distant supernovae, which do in fact emit the energy that gave birth to stars, galaxies and the material that makes up our universe.
The Milky Way is really the galaxy where our sun hangs out. And the sun is not the only star in the Milky Way, and the Milky Way is not the only galaxy in the universe. Astronomers have long since been in the quest to find out exactly how many galaxies there are in the universe, and you won’t believe the numbers they’ve come up with! With time, as humans progressed, the scope of what we considered the universe also advanced.
First, we thought that the earth we lived on, the Sun, the Moon and the stars that we could see with our naked eyes made up the entire universe. So, effectively, for a large part of human history, we considered the Milky Way to be the only universe.
We thought that all the stars that we see belong to it. This belief didn’t change until the 1900s when scientists like Henrietta Swan Leavitt and Edwin Hubble identified stars whose brightness seemed to change when observed from the earth. They called these the Variable Stars.
Leavitt had intensely studied thousands of Variable stars. She found that certain stars, called Cepheid variables, have the same brightness if they twinkle at the same speed. This discovery proved to be a milestone in measuring the distance of stars and galaxies.
It provided a way to relate brightness to distance. Then came Hubble, who, using the Hooker telescope at Mount Wilson Observatory, California, identified several of these variable stars.
- He then used some complex mathematics to calculate the distance of these stars.
- His calculations showed that these stars were way too distant to belong to our galaxy.
So, he concluded that they must be members of some other faraway galaxies and not the Milky Way. This discovery motivated astronomers to find out exactly how many galaxies are out there in the universe. To aid this mission, more and more powerful telescopes were developed.
Today we have telescopes both on the ground, and in outer space, that regularly stare into the vast universe to detect the faintest and most distant galaxies.
Hubble Space Telescope
A major contributor to this quest, and towards making astronomy popular, is the Hubble Space Telescope. Named after famous astronomer Edwin Hubble, this telescope was launched into the low Earth orbit in 1990 and remains operational.
It tried to investigate deep space for the first time in 1995. The image that the telescope captured is known as the Hubble Deep Field, and in it, scientists could identify 3000 distinct galaxies.
Similar deep observations using the Hubble and other telescopes followed its success, and they found even more galaxies.
Using these experiments, scientists determined that there are about 125 billion galaxies. But that large number appears faint compared to what scientists would discover a few years later.
In 2016, a study conducted by a team of astronomers, led by an astrophysicist from the University of Nottingham, used 3D modeling of images collected over 20 years by the Hubble Space Telescope to determine the number of galaxies.
What they found was startling.
According to them, there are over 2 trillion galaxies. These galaxies lie in what is known as the observable universe. The observable universe is the part of the universe that can be seen from Earth or from space-based telescopes like the Hubble.
Right now, it’s 93 billion light-years in diameter. These galaxies are those from which light has reached us since the beginning of the universe.
Have we blown your mind yet?
Well, hang on… Improved technology in finding the light that’s not visible to human eyes has now made it possible for us to reveal galaxies that couldn’t be detected by Hubble.
These galaxies mostly lie in an area called the Zone of Avoidance; that is, the region in the sky that’s obscured by the Milky Way.
The farthest galaxy that we’ve been able to observe till now is named EGS-zs8-1. I think we should nickname it “bob”. It’s so far out that the light from there took a little over 13 billion years to reach us.
We studied in our Physics class that we can’t see an object until its light reaches us. And although light travels extremely fast, it still takes time to cover such long distances. For example, the light from our Sun, which is just about 93 million miles away from the Earth, takes 8 minutes and 20 seconds to get here. And so, if the light from the nearest star, Alpha Centauri, takes more than 4 years to reach us, it means we’re seeing that star 4 years in the past.
The light you see from your computer or your smartphone screen is just nanoseconds old. So, now let’s go back to the farthest known galaxy, the EGS-zs8-1, or Bob. Since its light took about 13 billion years to reach us, it means that what we see of this galaxy today is how the galaxy looked about 13 billion years ago, long before the earth, or even our sun, came into existence.
The discovery of such galaxies has helped astronomers to understand how the universe began and how it’s evolved since then. It’s now generally accepted that the universe is about 13.8 billion years old; so the galaxy Bob is certainly one of the earliest galaxies to have formed in the cosmos.
Looking at it is like looking at the universe’s past. A very fascinating, and yet sometimes confusing, aspect of the Mysterious universe is that its size is not permanent. Instead, it’s been growing ever since it was created by the Big Bang. And the farther an object is from us, the faster it’s moving away from us.
So, by the time light from a faraway galaxy reaches us, the same galaxy has already moved farther away. This makes it difficult to calculate the actual distance of faraway galaxies, because by the time we see them, the distance has changed.
So, according to some complex calculations, the most distant galaxy is about 32 billion light-years away from us now, and is still moving away from us, picking up speed as it goes.
The expanding universe theory also means that there’s a point in the universe from which things are moving away from us at a speed faster than the speed of light; a point beyond which, given our current scientific knowledge and technology, we can’t investigate.
This is a place from where light can never reach us. The enormous blue star nicknamed Icarus is the farthest individual star we’ve seen to date.
Normally, it would’ve been too faint to view, even with the largest and most powerful telescopes that we have today. But it seems like nature wanted us to have a look at it. It was because of a fluke of nature that the star’s weak glow got extremely bright.
Astronomers using NASA’s Hubble Space Telescope were, therefore, able to pinpoint this faraway star and set a new distance record.
The star is in a very distant spiral galaxy. It’s so far away that its light took 9 billion years to reach Earth. All these discoveries have been amazing. But scientists are never satisfied with what they know or have. They have an unquenchable thirst to know and develop new things. So, to look at objects far, far away, and more difficult to be detected by telescopes, they developed an observation network in the Netherlands that can see light sources that regular telescopes can’t.
This newer telescope works by detecting radiation produced by the interaction of huge cosmic objects. This telescope network is called Low-Frequency Array or LOFAR. Over 200 scientists from 18 different countries teemed in an awe-inspiring study, using radio astronomy to analyze a tiny section of sky above the northern hemisphere.
During this experiment, they were able to identify 300,000 new galaxies. But even with such advanced systems, scientists say that they’ve only been able to chart 2 percent of the sky so far.
The team of scientists now plan to set their eyes on the entire northern sky. They hope to be able to discover many more new galaxies that can shed light on various other research areas, including the physics of black holes as well as research into how galaxy clusters evolve.
But will we stop with the LOFAR systems?
If there’s been something constant in the evolution of humans, it’s the fact that we’ve always made progress. And with time, the rate of this progress has only sped up.
The universe, as I see it, is far vaster than we can ever discover, but it surely doesn’t discourage those searching; it’ll only make them push harder. It wouldn’t surprise me if, someday soon, we discover even more galaxies at even farther distances.
What about you?
Do you think we will discover more galaxies than we have till now, before the end of the decade?
Let me know down in the comments! If you learned something new, then share it with a friend. But – hey! – don’t go star trekking just yet! We have over 150 cool articles for you to check out – right here on Earth. Click on it, and enjoy it! Stay on the Bright Side of life!
Also Read: How Many Universe Are There?