Structures of the universeThe matter in the universe is sorted. The force of gravity causes that matter group forming structures. From the simplest, like the stars and solar systems, to the gigantic walls of galaxies. Even so, the expansion of the universe makes that different structures to radically depart from each other at high speed.
The more distant structures are the largest and oldest. They were formed when the universe was still very young, and help to understand its evolution.
Hierarchy of structuresSmaller structures: are bodies celestial, as planets and stars, and the small groupings, such as our Solar System.
Galaxies: are intermediate structures. They gather families of stars, gas, dust, and dark matter. There are more than 100 billion only in the visible universe, and they can group trillions of stars. Many have a black hole at its Center. Our Galaxy is the milky way.
Clusters of galaxies: are groups of galaxies involved in hot gas. Their diameter reaches several million years light. Star Wars revolve one around each other, linked by gravity. Sometimes they collide or some are absorbed to others. The milky way belongs to a cluster called the Local Group, comprising 25 galaxies.
Superclusters of galaxies: They are sets of clusters of galaxies. They measure hundreds of millions of light years. They form large layers throughout the visible universe. The Local Group is part of the Virgo supercluster.
Walls: these are the last discovered structures, the most ancient and large universe. They are huge swaths of Superclusters of galaxies. Sloan great wall measures 1.37 billion years light and is the largest structure that is known.
The great attractorThe Virgo supercluster and the other structures of the visible universe moving towards a mysterious point called the great attractor. Its centre is 150 million years light. It was discovered in the late 1980s and is not yet known what it is, although it might be one structure even more that astronomers call Laniakea ("sky immense", in Hawaiian).
Translation for educational purposes authorized by: Astronomía: Tierra, Sistema Solar y Universo