Observable Universe

No one knows for sure how big the Universe really is. Scientists have made many attempts to observe the Universe and peek to the furthest parts of it.

To date, the best equipment available for observing the Universe is The Hubble Telescope, which is orbiting the Earth and taking pictures of the deep space and sending them back to us. These images shows that there are billions and billions of galaxies. Each galaxy contains many billions of stars, many of which have planets around them.

Let’s try and understand where we with our planet are positioned in the Universe, or at least the observable Universe – the one we can actually see.

 

As you all know, we live on planet Earth:

 

 

Our planet, along with other 7 planets, circles the closest star – the Sun. We call it the Solar System, and it contains 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), several asteroids (Pluto being the biggest one of them) and of course the Sun:

 

 

There is a number of stars in our direct neighbourhood, which we call “Solar Interstellar Neighbourhood”. Although we call it “neighbourhood” the closest star (Alpha Centauri, which in fact is two stars circling each other) is 4 lightyears away from us. This means that it takes 4 years for a beam of light to reach us. No physical body can travel at this speed or even half of it. The scientists have plans of building spaceships that could reach 1/10th of this speed, but it would be too expensive to build. Even if we did build it, it would take more than 40 years for it to reach Alpha Centauri. So we’re not ready yet to visit our neighbours:

 

 

As you already know, stars concentrate in a group called galaxy. There could be billions of stars in each galaxy. Our Sun belongs to a galaxy, which we call the Milky Way Galaxy. The scientists think there might be 100 to 400 billion stars in this galaxy, with over 50 billion planets. It is called the Milky Way, because we can only see the pale band of light coming from all the stars in the galaxy. The name derives from latin Via Lactea, which means Road of Milk. The reason we can see pretty much all of the galaxy is because our Sun is located near its edge. All stars in our galaxy rotates around its centre. It takes one galaxy year for our sun to make a full circle. One galaxy year is approximately 250 million Earth years.

 

 

Just like our Sun has its direct neighbours, our galaxy has its neighbour galaxies too. We call this neighbourhood Local Galactic Group, and it is made of 56 galaxies that are relatively close to each other:

 

 

As you may have already guessed, there are more galaxy groups, just like our Local Galaxy Group. These groups form another group of it’s own and it is called Virgo Supercluster. It is estimated that there are approximately 100 local groups in this supercluster:

 

 

Similarly, there are multiple superclusters like that, and they form another group that contains multiple superclusters. There is approximately 50 superclusters in this group:

 

 

And finally, all Local Superclusters form what we call the Observable Universe. The Observable Universe is the universe that we can observe from our planet. The real Universe might be bigger than the Observable Universe, but we can only guess how bit it it. From what we know the real Universe goes on and on, and might be infinite. The reason why we cannot see beyond the Observable Universe boundaries is that we can only observe the light that comes from the distant stars. Because our Universe has limited age (the scientists think it is 13 billion years) we can only see as far as this distance. In other words, if there is anything beyond this distance we simply cannot see it, because the light from the stars beyond this distance has not arrived to the Earth yet:

 

Now take a flight from our Earth, through the space, to the edge of our Universe (and back!!):