What is a galaxy?
The solar system we are in cannot be considered a galaxy, it is just an stellar system . In our opinion, the solar system is very large. This "huge" star system has one star, 8 planets, 173 planets satellite , and a large number of dwarf planets , asteroids and other celestial bodies. But it is such a "huge" star system. It is just a dust-like existence in Milky Way , because there are hundreds of billions of stars in the Milky Way, and there are some big guys among these stars, and their mass can reach hundreds of times that of Sun Mass . So, how big is such a galaxy with hundreds of billions of stars? Its diameter is about 150,000 light-years, while our solar system is about 26,000 light-years away from the center of the Milky Way.
The Milky Way is a very huge cosmic structure, but such a huge cosmic structure is not rare in the universe.
Not to mention the distance, there is a galaxy larger than the Milky Way near the Milky Way. We call it "Andromeda Galaxy". It is the closest galaxy to us outside the Milky Way. It is about 2.54 million light years away from us, which means it takes 2.54 million years for its light to reach the earth. The Andromeda Galaxy we are seeing now is a scene 2.54 million years ago. There are dozens of galaxies of all sizes around the Milky Way and Andromeda galaxies. These galaxies form a larger celestial system, , and galaxy group. We call this galaxy group " galaxy group ".
The diameter of a galaxy reaches tens of thousands, or even hundreds of thousands of light years, and the distance between galaxies must be calculated in "millions of light years". It goes without saying how huge the galaxy group composed of nearly 50 galaxies is.
However, "galaxy clusters" are not rare things in the universe, and there is a larger celestial structure above them, which we call " super galaxy clusters ". A supercluster is usually composed of hundreds of galaxies. Taking the supercluster we are in as an example, it is composed of more than 100 galaxies. We call this supercluster " VIV supercluster ". The Virgo supergalaxy cluster is not an approximately circular structure, but is a distinct elliptical shape. Its length reaches 100 million to 200 million light-years, with more than 2,500 galaxies.
00 million light years, which is an unattainable distance for us, but for the universe, such a celestial structure is just a speck of dust.
If the entire observable universe is represented by an A4 paper, then a small dot on the center of the paper can probably represent the Virgo super galaxy cluster. The observable universe has a radius of about 46.5 billion light years. So how many galaxies are there in the observable universe? We do not have the ability to obtain accurate data yet, but scientists estimate that within such a huge range, it can accommodate up to 2 trillion galaxies, or at least not less than 200 billion. With so many galaxies, and there are hundreds of billions of stars in each galaxy, it seems that there are indeed more stars in the universe than the sand on the earth.
We have already experienced the greatness of the universe, but this is just an observable universe.
The observable universe's radius is 46.5 billion light years because of the limitation of the speed of light and the expansion of the universe. We can only see things within this range. In addition to the observable universe, there is a broader space, and the space there is still expanding. So no one knows how big the universe is, how many galaxies are there, and how many stars are there, and it is very likely that no one will know.The greatness of the universe not only transcends our imagination, but also transcends our ability to understand. Therefore, whenever we look up at the stars and let our hearts talk to the deep universe, we will truly appreciate our own insignificance, and all the hardships in front of us will become insignificant.
