Absorption spectrum of galaxy
The above are the absorption spectra of galaxy A and galaxy B, which were observed at our galaxy, as compared to the absorption spectrum of the sun. Which of the following statements is correct?
a) Galaxy A and galaxy B show a red shift of the spectrum.
b) The rate of increase in the distance of galaxy B from the earth is faster than that of galaxy A.
c) The distance of galaxy A from our galaxy is larger than that of galaxy B.
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1 solution
The three objects have the same 5 lines since they are the absorption lines of hydrogen. Our star is 'fixed' since the stretching of space is not noticeable on the scale of the solar system.
Hubble discovered that space is expanding and the farther an object is, the faster it is receding from us. And this speed is increasing. This speed is seen in the absorption spectrum as a redshift. Red is to the right and compared to the sun the galaxies are shifted to the right. Hence a) is correct.
Also, Galaxy B is shifted more, so b) is also correct as well.