Apparent Magnitude and Intensity Formula

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Discussion Overview

The discussion revolves around the formula relating the intensities of two stars to their apparent magnitudes, specifically questioning the correct formulation and understanding of the relationship between intensity and magnitude in the context of astronomy.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the formula Ia/Ib=2.512^(Mb-Ma) and suggests it should be Ia/Ib=(2.512)^(Ma-Mb), based on their understanding of the definitions of Ia and Ib.
  • Another participant explains that magnitude is an "inverse" scale, indicating that a minus sign is missing in the initial formulas presented.
  • A participant expresses gratitude and seeks clarification on the relative intensity of a magnitude 5 star compared to a magnitude 0 star, suggesting it is 0.1.
  • Another participant corrects the previous claim, stating that the actual relative intensity is 0.01, explaining that the scale is defined by a ratio of 100 for a difference of 5 magnitudes.

Areas of Agreement / Disagreement

Participants express differing views on the correct formulation of the intensity-magnitude relationship, with no consensus reached on the correct interpretation of the formula or the implications of the magnitude scale.

Contextual Notes

There are unresolved aspects regarding the definitions of intensity and magnitude, as well as the implications of the inverse nature of the magnitude scale, which may affect the understanding of the formula.

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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