Apparent Magnitude and Intensity Formula

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SUMMARY

The formula for comparing the intensities of two stars, represented as Ia/Ib = 2.512^(Mb-Ma), is established based on the definition of apparent magnitude. The apparent magnitude scale is logarithmic and inverse, where a difference of 5 magnitudes corresponds to a factor of 100 in intensity. The initial confusion regarding the formula was clarified by noting that the correct relationship involves the magnitudes of the stars being subtracted in the order of their apparent brightness. The discussion emphasizes the importance of understanding the logarithmic nature of the magnitude scale in astrophysics.

PREREQUISITES
  • Understanding of logarithmic scales in mathematics
  • Familiarity with the concept of apparent magnitude in astronomy
  • Basic knowledge of star intensity and brightness comparison
  • Ability to interpret scientific formulas and equations
NEXT STEPS
  • Research the derivation of the apparent magnitude formula in astrophysics
  • Explore the relationship between magnitude differences and intensity ratios
  • Learn about the history and applications of the magnitude scale in astronomy
  • Investigate the effects of distance and interstellar medium on star brightness
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Astronomy students, astrophysicists, and anyone interested in understanding stellar brightness and the mathematical relationships governing apparent magnitudes.

thegirl
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Hey,
Could anyone explain why Ia/Ib=2.512^(Mb-Ma), Where "Ia" and "Ib" are intensities of star a and star b and "Mb" and "Ma" are the apparent magnitudes of star A and star B?

I thought the formula would be Ia/Ib=(2.512)^(Ma-Mb) because Ia=2.512^Ma and Ib=2.512^Mb.

Thank You
 
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Magnitude is an "inverse" scale in this sense : magnitude 0 is very bright (about the brightest visible stars), magnitude 10 is very faint (invisible naked eye). There's a minus sign missing in your formulas for la, lb.
 
Last edited:
Thank you so much! So the actual relative intensity of magnitude 5 is 0.1 relative to the apparent magnitude 0?

Thanks again!
 
Thank You!
 

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