Observations of quasars have shown us that many are extremely _________, emitting more energy than all the stars in a galaxy. The energy they give off comes from a very small volume, typically about the size of ___________. Some have long ______, shooting off in opposite directions. Today, astronomers understand that all the properties of quasars can be explained if they are __________ at the centers of galaxies. Astronomers can use _____________ to study images and spectra of the central regions of galaxies more clearly than earlier instruments.
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.
Observations of quasars have shown us that many are extremely _________, emitting more energy than all the stars in a galaxy. The energy they give off comes from a very small volume, typically about the size of ___________. Some have long ______, shooting off in opposite directions. Today, astronomers understand that all the properties of quasars can be explained if they are __________ at the centers of galaxies. Astronomers can use _____________ to study images and spectra of the central regions of galaxies more clearly than earlier instruments.
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