Question

Altair in the constellation Cygnus is 16.4 LY distant with an apparent magnitude m = +0.8 and absolute magnitude M = +2.3. Verify its absolute magnitude using the inverse square law for light.

Answer 1

Answer on question #54919, Physics / Astronomy — Astrophysics

Question Altair in the constellation Cygnus is 16.4 LY distant with an apparent magnitude m = +0.8 and absolute magnitude M = +2.3. Verify its absolute magnitude using the inverse square law for light.

Solution Apparent $m$ and absolute $M$ magnitudes are related as

$M=m-5((\log_{10}D_{L})-1)$

where $D_{L}$ is distance in parsecs. In our case $D_{L}\approx 5.028$ pc. Hence

$M=0.8-5((\log_{10}5.028)-1)=0.8+1.5=2.3$

Indeed, absolute magnitude is 2.3.

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