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# how much brighter is the star Procyon (with an apparent mag of 0.38) than Capella (with an app mag of .08)?

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I am not sure how i am supposed to solve this and i just need guidance on how to go about the problem. i know that each integer increases by 2.5 and that the lower the brighter, but is it the lower the brighter for apparent mag or absolute mag? Because in my book it shows the suns apparent magnitude as -26.7 and abs. as 5, and then it says antares ap as .9 and abs as -5.1.Cause with apparent the suns brighter and with absolute antares is brighter??So confused I need to just focus on apparent but

Nov 17th, 2017

Hi,

So in both cases lower is brighter. The *absolute* brightness of the sun is a good deal lower than many other stars, including Antares (which is an extremely large and bright star with a volume almost a billion times greater than the sun: http://en.wikipedia.org/wiki/Antares). Think of absolute magnitude as being the amount of light emitted by the star.

But, of course, apparent brightness is a function of both absolute magnitude and distance from the star (think of it as the amount of light reaching your eye). So because the sun is so many orders of magnitude closer to us than any other star (about 250,000 times closer) and the proportion of light hitting your eye decreases with the square of the distance, the sun greatly outshines everything else on Earth. Just don't let that fool you into thinking the sun is especially bright compared to the other stars you can see in the night sky!

To calculate the difference in magnitude, use the base 2.512 (arbitrary, and a holdover from the Greeks I think). This means:

Brightness ratio = 2.512^(magnitude difference)

= 2.512^(.30)

= 1.318

Apr 5th, 2015

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Nov 17th, 2017
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Nov 17th, 2017
Nov 18th, 2017
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