cientists observe a distant galaxy with a spectrometer. They find that the wavelength of the Lymann alpha Hydrogen line in the stars spectrum has shifted from its laboratory value of 121.6 nm to three times that value, 364.8 nm. According to the doppler effect, how fast is the galaxy receeding from us? (Find v/c of the galaxy relative to us).
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.
Scientists observe a distant galaxy with a spectrometer. They find that the wavelength of the Lymann alpha Hydrogen line in the stars spectrum has shifted from its laboratory value of 121.6 nm to three times that value, 364.8 nm. According to the doppler effect, how fast is the galaxy receeding from us? (Find v/c of the galaxy relative to us).
The wavelength is increasing so frequency is decreasing since wavelength is inversely proportional to frequency.
initial wavelength
shifted wavelength .
for source moving away from the observer the frequency is given by where is the initial frequency and f is shifted frequency.
since wavelength is inversely proportional to frequency( ,where c is speed of light).
The above equation becomes
Now applying the given values we get
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