1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

  1. Mar 14, 2007 #1
    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!
     
  2. jcsd
  3. Mar 14, 2007 #2

    Mentz114

    User Avatar
    Gold Member

    H0 is the Hubble constant, here.
     
  4. Mar 14, 2007 #3
    yes it is ....
     
  5. Mar 14, 2007 #4

    Mentz114

    User Avatar
    Gold Member

    Use
    Z(redshift)= (wavelength observed-wavelength emitted) / wavelength emitted
     
  6. Mar 14, 2007 #5
    yea but i dont have 'wavelenght emitted'... i only have wavelenght observed :S
     
  7. Mar 14, 2007 #6

    Mentz114

    User Avatar
    Gold Member

    Wavelength emitted is given as

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

    look it up.
     
  8. Mar 14, 2007 #7
    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
     
  9. Mar 14, 2007 #8
    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_)
     
  10. Mar 14, 2007 #9

    Mentz114

    User Avatar
    Gold Member

    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.
     
    Last edited: Mar 14, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: What is the redshift and velocity of the galaxy relative to us
Loading...