Is My Approach to Finding Absolute Magnitude Correct?

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The discussion revolves around the correct approach to calculating absolute magnitude using specific equations. A participant initially made an error by changing a factor from 2.5 to 5 in their calculations, which was pointed out as a mistake. After correcting the exponential and addressing a sign error, the calculations were confirmed to be on the right track. The final analysis indicated that the star's absolute magnitude is smaller than the Sun's, suggesting it has a greater luminosity. Overall, the steps taken were validated, and the participant was encouraged to proceed with their calculations.
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Homework Statement


1.2.png
[/B]

Homework Equations


m1-m2[/SB]=2.5log(ι2/ι1)

m-M=2.5log (d/10)2

3. The Attempt at a Solution
1.2 answer.png


Not sure if my approach and answers are correct

Please help
 
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shanepitts said:

Homework Statement


View attachment 83971 [/B]

Homework Equations


m1-m2[/SB]=2.5log(ι2/ι1)

m-M=2.5log (d/10)2

3. The Attempt at a Solution
View attachment 83972

Not sure if my approach and answers are correct

Please help
First question: In your very first line with an equation, you changed the factor of 2.5 to a factor of 5 in front of the log. Why did you do this? This seems to be a mistake.
 
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nrqed said:
First question: In your very first line with an equation, you changed the factor of 2.5 to a factor of 5 in front of the log. Why did you do this? This seems to be a mistake.

I forgot the exponential: m-M=2.5log(d/10)2
 
shanepitts said:
I forgot the exponential: m-M=2.5log(d/10)2
AH yes, Ok.

EDIT: you seem to have made a sign mistake. In the exponential for the calculation of the luminosity, you should have

M_1 - M_2 = M_1 - ( m +1.99) = 5 -m - 1.99


Then your work looks good. You just need to plug in the value of m=2. The absolute magnitude of the star is smaller than the Sun's absolute magnitude (3.99 versus 5) so the star has a larger luminosity than the Sun's and your final expression agrees with this. All the steps look good.
 
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nrqed said:
AH yes, Ok.

EDIT: you seem to have made a sign mistake. In the exponential for the calculation of the luminosity, you should have

M_1 - M_2 = M_1 - ( m +1.99) = 5 -m - 1.99Then your work looks good. You just need to plug in the value of m=2. The absolute magnitude of the star is smaller than the Sun's absolute magnitude (3.99 versus 5) so the star has a larger luminosity than the Sun's and your final expression agrees with this. All the steps look good.

Thanks a bunch and sorry for the typo
 
shanepitts said:
Thanks a bunch and sorry for the typo
You are welcome. And no problem about the typo, I make typos all the time :-)

Patrick
 
Last edited:

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