Stellar evolution
We may see thousands of stars in the dark sky. Our universe consists of billions of stars. Stars may appear tiny to us but they are huge balls of gasses. Sun is a star of average size. Some stars are even a thousand times larger than the sun. The stars do not exist forever they have a certain lifetime. The life span of the sun is about 10 billion years. The star undergoes various changes during its lifetime, this process is called stellar evolution. The structure of the sun-like star is shown below.
Red Shift
It is an astronomical phenomenon. In this phenomenon, increase in wavelength with corresponding decrease in photon energy and frequency of radiation of light. It is the displacement of spectrum of any kind of astronomical object to the longer wavelengths (red) side.
What is our "cosmic address"?
When give your address to somebody, you want to make sure you can be found. Earth is a part of the solar system. Within the galaxy a good idea would be to give location as set of distances to nearest pulsars.
Our cosmic address:
Planet Earth, Solar system, 2300 light year from the centre of our galaxy. Your home or your school has an address: a street, a city or town, and a country. When someone wants to send you a letter, they give your address, so that your mail carrier knows the letter should go to you.
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