11-3 Absolute Magnitudes and Luminosities

Question 1

absolute magnitude (M)

Answer 1

a measure of the total energy emitted by a star, independent of distance to us.

Question 2

how to calculate absolute magnitude

Answer 2

it is necessary to know the distance of the star and apparent brightness. apparent brightness m decreases inversely with the square of the distance between the source and the observer. M is the apparent brightness corrected by the distance. is the brightness a star would have if it were at a distance of 10 pc from us

Question 3

the inverse-square law

Answer 3

the same amount of radiation from a light source must illuminate an ever-increasing area as the distance from the light source increases. the decrease in brightness follows the inverse-square law. for example, tripling the distance decreases the brightness by a factor between 3^2=9

Question 4

the distance-magnitude relationship

Answer 4

M = m - 5log (d/10)

m - M = 5logd - 5