# What is the redshift and velocity of the galaxy relative to us

hey everyone... so im tryna solve this problem :

a galaxy shows an emission line at a wavelenght of 6610.2 A, which we identify as the H-alpha line in the Balmer series of Hydrogen. what is the redshift and velocity of the galaxy relative to us.

period= 4.3 days
magnitude= 26.25
absolute magnitude= -3.21
distance= 7 800 000

okay so my main problem is trying to get planck's constant. I'm tryna use v(redshift velocity)=H0(planck's constant) * D

OR should i use Z(redshift)= (wavelenght observed-wavelenght emitted) / wavelenght emitted

thanks!

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H0 is the Hubble constant, here.

yes it is ....

Use
Z(redshift)= (wavelength observed-wavelength emitted) / wavelength emitted

yea but i dont have 'wavelenght emitted'... i only have wavelenght observed :S

Wavelength emitted is given as

"H-alpha line in the Balmer series of Hydrogen"

look it up.

the wavelenght is not exact... and thats not what they meant by that (i think?) cuz they gave the wavelenght and i think they just mentioned the balmer series for clarification... at a wavelenght of 6610.2 A, which we identify as the H-alpha line

okay i re-did the problem and now i have these values:

distance = 29.46 m
M (absolute magnitude)= -3.21
period= 4.3 days
m(magnitude)= 26.25

i just cant seem to find an equation WITHOUT another value for wavelenght (emitted wavelenght value_)

The whole point about red-shift measurements is to get the frequency difference. The emitted frequency is different and we can measure it here on earth and compare with what we received.

Your post #7 is just wrong.

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