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1)A certain star is moving towards the earth at a velocity of 262 km/s. What can we expect to measure for a spectral line, normally found at 815.1 nm?
2)Star B is 41 Mega light years away from us. How fast is Star B receding from Earth in km/s?
3)We measure the velocity of Star A to be 404.5 km/s. How far away is Star A in Mega parsecs?
a certian star
velocity towards earth, v = 262,000 m/s
a. lambdao = 815.1 nm
as the light source is moving towards the earth, it will appear to be blue shifted
v/c = (lambdao - lambda)/lambdao = 1 - lambda/lambdao
262,000/3*10^8 = 1 - lambda/815.1
observed lambda = 814.38814 nm
b. given d = 41*10^6 ly
form hubbles law
v = Hod
Ho = 71 km/s Mpc
d = 12.57 Mpc
v = 892.47 km/s
c. Va = 404.5 km/s
distacne from earth = d
v = Ho*d
d = v/Ho = 5.697183 parsecs
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