The Milky Way is our galaxy. One of the billions of galaxies in our universes. And it’s huge. Measuring about a 150,000 light years across, it can be called a large galaxy. But is it the largest??
Before I answer that question let us first understand what a light year is to get a true sense of scale. Otherwise all this will just seem like a post with giant numbers.
Light travels at a speed of 300,000 km per second. So in just one second light can circle the entire Earth with a diameter of 12,756 kms about 7 times!!
To give an even better sense of the size and enormity involved while talking about the Universe, consider this.
The distance between the Earth and the Sun, which is about 250 million kms, is covered by light in about 8 minutes. If that’s not enough, think again. At a super fast speed of 300,000 kms per sec it still takes light 8 minutes to travel from the Sun to the Earth.
Now extend that to the Solar System. Light takes about 5 hours to reach Neptune and that’s not even close to the official end of the Solar System which is covered by light in about half a year.
So we will define the distance covered by light in one year as one light year. Convert it to kilometers and it’s about 9.5 trillion kms. That’s bigger than the entire Solar System!!
Thus now maybe you can get a feel of the monstrosity of the Milky Way’s size. 150,000 light years!! So if a light ray left one corner of the galaxy when the first humans walked the Earth, it would reach the other end now.
But if you think this size is incomprehensible, wait till you meet the biggest galaxy. It even puts our Milky Way to shame. Meet IC 1101: the largest known galaxy in the Universe.
IC 1101 is an elliptical galaxy located 1.04 billion light years away from Earth in the Abell 2029 galaxy cluster. It was discovered by British astronomer Frederick William Herschel 1 in 1790. At that time it was just considered another nebula in our own galaxy until its true nature was known many years later. And what was found was truly mind-boggling.
Measuring at a whopping 6 million light years in diameter, IC 1101 is 40 times the size of the Milky Way. If you hate numbers, this image is for you.
Now you feel small don’t you?? To appreciate this even further let us consider the distance between the Milky Way and Andromeda, the closest galaxy to us. This is about 2.5 million light years.
So if IC 1101 was placed where Andromeda is, it would cover up not only Andromeda but also the Milky Way as a whole and surrounding galaxies in the neighborhood.
But it is theorized that it wasn’t always like this. This enormous size is thought to be the result of many galaxies colliding into each other to form this one giant monster. This just shows how galaxies interact on the wide scale and how it determines their properties.
These collisions have stripped of all the clouds of gas and dust from the galaxy with no more active star formation taking place. This means that the galaxy is composed mostly of old stars which will die off in a few million years; a relatively short time compared to the total life of stars.
As these stars slowly die off, the galaxy will slowly shrink and one day might completely disappear.
However that day is quite far in human standards, about a few billion years or so. Hence IC 1101 still has quite some time to boast about its title unless there is an even bigger monster out there we just haven’t discovered. We may never know.