Question

There are two ways to measure the brightness of a star; the apparent magnitude of the brightness of the star is the brightness seen from the earth and absolute magnitude of the brightness of the star which is the brightness of a star seen from the standard distance of ____________.
(A) 10 parsecs
(B) 32.6 light years
(C) 3.26 light years
(D) Both (a) and (b)

Answer 1

Hint: To answer this question we should have a clear concept about the light years. It is a measuring unit of the distance covered by light. On the basis of the numerical values that light years signifies we can answer to the required question.

Complete step by step answer:
We should know that astronomers define star brightness in terms of apparent magnitude, how much bright the star appears from the Earth, and the absolute magnitude, how much bright the star appears at a standard distance of 32.6 light years or 10 parsecs.
Hence we can say that there are two ways to measure the brightness of a star; the apparent magnitude of the brightness of the star is the brightness seen from the earth and absolute magnitude of the brightness of the star which is the brightness of a star seen from the standard distance of 32.6 light years or 10 parsecs.

So the correct answer is both (a) and (b). Therefore, we can write option D is correct.

Note: We should know that a light year is defined as the distance that is travelled by light in one year. This distance is about 6 trillion miles or 10 trillion kilometres. Astronomers also measure the luminosity, the amount of energy, that is light that will be emitted from the surface.
It should be known to us that measuring the star brightness is an old method. At present the astronomers use various kinds of tools to achieve the calculation.
One light year can be said as 9,500,000,000,000 kilometres. The speed of light is considered to be 300,000 kilometres each second.