We see different kinds of natural bodies like the sun, the stars, the moon, and so on. The natural bodies in the sky are called celestial bodies or heavenly bodies. They are part of our universe. The universe is a huge space which contains everything that exists. The celestial bodies that we see are just a small fraction of the bodies that exist in the universe. One of the reasons why we do not see more of them is that they are very, very far away.

To measure the large distances in the universe, scientists use a unit of length called the light year. A light year is the distance travelled by light in one year. Light travels 9.46 trillion km in a year (one trillion is 1 followed by 12 zeroes).

When we look at the sky, we see different kinds of natural bodies like the sun, the stars, the moon, and so on. The natural bodies in the sky are called celestial bodies or heavenly bodies. They are part of our universe. The universe is a huge space which contains everything that exists. The celestial bodies that we see are just a small fraction of the bodies that exist in the universe. One of the reasons why we do not see more of them is that they are very, very far away.

To measure the large distances in the universe, scientists use a unit of length called the light year. A light year is the distance travelled by light in one year. Light travels 9.46 trillion km in a year (one trillion is 1 followed by 12 zeroes).