All the elements on Earth, including all the elements in our body, were produced in stars.

The universe (Latin: universus) is all of space and time and their contents, including planets, starsgalaxies, clusters, super-cluster, voids, and all other forms of matter and energy. While the spatial size of the entire universe is unknown, it is possible to measure the size of the observable universe, which is currently estimated to be 93 billion light-years in diameter.

We see objects in space because of their light. Stars produce their own light but others such as planets, Moon, shine by reflecting light.

Speed of Light - The Universe

Contents of The Universe

The universe consists of planets, starsgalaxies, clusters, super-cluster, voids, and all other forms of matter and energy.

  • Planet: planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity. Our planet Earth may feel big to us but at 12,756 Km (7926 Miles) across, it is just a speck in an expanding Universe.

  • Star:star is an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to the Earth is Sun. Without it, there would be no life. Its diameter is about 1.39 million kilometers (864,000 miles), or 109 times that of Earth, and its mass is about 330,000 times that of Earth.

  • Galaxy: A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. Stars exist in galaxies, colossal star systems that come in a range of sizes and shapes. Our solar system is in the Milky Way Galaxy.

  • Cluster: A cluster is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity with typical masses ranging from 1014–1015 solar masses. The Milky Way Galaxy is in the Local Group Cluster, stretching 10 million light-years across. They are the largest known gravitationally bound structures in the universe and were believed to be the largest known structures in the universe until the 1980s when superclusters were discovered.

  • Supercluster:supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest known structures of the Universe. We are in Virgo Supercluster (sized 200 million light-years from one side to the other) which in turn is a part of the Laniakea Supercluster.

  • Voids: Cosmic voids are vast spaces between chains of superclusters (the largest structures in the universe), which contain very few or no galaxies. Voids typically have a diameter of 10 to 100 megaparsecs; particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids.

Lightyear - The Universe

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