Answer:
c. as seen from the Earth without the effect of the atmosphere
Explanation:
The stars and objects in the sky emit light that, regardless of the distance they are, reaches us with greater or less intensity, being brighter the closer, larger, and / or higher temperature they have, and vice versa. This luminosity is called magnitude, and it is known that since ancient civilizations it was classified by the intensity of its brightness.
The apparent magnitude is the luminosity that the object shows us as it is seen in the sky, regardless of the temperature, the size or the distance at which it is located, and it is expressed with a number that can result, depending on the brightness , positive or negative, being brighter the smaller that number is (an object with a negative magnitude will always be brighter than one with a positive magnitude).
We can verify that, as we said at the beginning of the entry, today we observe magnitudes that are far from the first to the sixth used by Hipparchus for its catalog. Later we will see what is being talked about here with some examples, although the fact that there are magnitudes with a negative value should already give you a clue as to what you will see.
