Worksheet: Note:u (v.M) distance modulus apparent magnitude minus absolute magni

Question

Worksheet: Note:u (v.M) distance modulus apparent magnitude minus absolute magnitude 1. Distance moduli as measured from your plot: us" 2. Distance modulus of cluster (average from 3 measured): 3. Distance of NGC 2287 as determined from its distance modulus: (Equation relating distance in parsecs to distance modulus.) (0.2H+1.0) (units po) r pc (As determined from above equation.) (Conversion from parsecs to light years.) r(ly) r(pc) x 3.26 ly/pc ly mhis is the value to use as rmeas below.) 4. Percent difference between measured distance and actual distance to NGC 2287 %dir. (reas-rada) x 100 ractuel 670 pc 2200 ly ractual difference 5. Question In the discussion it was stated that starlight from NGC 2287 does not suffer from interstellar extinction. How would the value of the measured distance change if there were some interstellar extinction? Explain.

Explanation / Answer

we consider three values of color index (.4 magnitude apart)

5.1= (10.3-1.2)= 9.1

2= (10.7-2.6)= 8.1

3= (11.4-3.6)= 7.8

6. distance modulus of cluster =(1+2+ 3)/3=8.34

using r =10^(.2 +1.0) we get

r= 465.58 PC

7. conversion of pc to light year

r(ly)=r(pc)* 3.26ly/pc= 465.58*3.26ly= 1517.81ly

8. % difference= 1517.81- 2200/2200*100= 31%

9. interstellar extinction is defined by two phenomena; absorption and scattering.Again extinction cause reddening of the particles and depends on ratio Rv= Av/E(B-V)

Usually we get the extinction at the steller population of 450Pc but in this case the population is 465.58pc and that means it is above the range of extinction.

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