If Vega is apparent magnitude zero, and Deneb first magnitude, then
A) Vega must be 2.5× hotter than Deneb.
B) Deneb must be a main sequence star, and Vega a giant.
C) Vega is about 100× brighter than Deneb.
D) Deneb is one magnitude brighter than Vega.
E) Vega is 2.5× brighter than Deneb.

Question

Quizplus · Accepted Answer

The apparent magnitude scale is logarithmic, where a difference of 1 magnitude corresponds to a brightness ratio of about 2.5 times. Since Vega is magnitude 0 and Deneb is magnitude 1, Vega is 2.5 times brighter than Deneb.

If Vega Is Apparent Magnitude Zero, and Deneb First Magnitude