A star, which is 2.1 x 1020 m from the center of a galaxy, revolves around that center once every 2.8 x 108 years. Assuming each star in the galaxy has a mass equal to the Sun's mass of 2.0 x 1030 kg, the stars are distributed uniformly in a sphere about the galactic center, and the star of interest is at the edge of that sphere, estimate the number of stars in the galaxy.
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.
A star, which is 2.1 x 1020 m from the center of a galaxy, revolves around that center once every 2.8 x 108 years. Assuming each star in the galaxy has a mass equal to the Sun's mass of 2.0 x 1030 kg, the stars are distributed uniformly in a sphere about the galactic center, and the star of interest is at the edge of that sphere, estimate the number of stars in the galaxy.
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