Which 'star' would be brighter?

Question

I had to do an experiment, but since my flashlight broke I can;t. :(

Anyway, which 'star' would be brighter- the larger one (the full flashlight beam) or the smaller star (the flashlight beam through a hole in the aluminum foil)?

Answer 1

The larger beam.
Brightness as it is in stars has two values. The Absolute Magnitude (M) tells how much energy the star is radiating. The Apparent Magnitude (m) tells how bright it appears to us. The difference is that Absolute Magnitude is always measured from the same distance (10 parsecs). Apparent Magnitude is measured from the earth and the distance to the star can vary quite a bit.
So the brightness is actually dependant on three things, size (the larger a light source is, the more light it can radiate), temperature (the hotter a light source is, the more light it radiates) and distance (the farther away a light source is, the dimmer it appears). If you use Absolute Magnitude, then you eleminate distance.
The luminocity of a star is porportional to R^2 x T^4 where R is the radius of the star and T is the temperature. As you can see, temperature plays a much bigger role than size.

Answer 2

Well the full flashlight would shine more light energy than would the pinhole flashlight. If you define brightness by how much total light energy you see then obviously the full flashlight would be brighter.