Question

question 2 of 19
consider the image. the stars in the antlia dwarf galaxy are all the same distance from earth.
if one star has an intrinsic luminosity of 1.9 lsun and a second star has an intrinsic luminosity of 7.3 lsun. which star appears brighter in the night sky?
the stars will have the same apparent brightness in the night sky.
the second star will appear brighter.
more information is needed to determine which star will appear brighter.
the first star will appear brighter.
stars in the antlia dwarf galaxy
although small, the antlia dwarf is a dynamic site featuring stars at many stages of evolution from young to old. the youngest stars are only found in the central regions where there is significant ongoing star formation. older stars and globular clusters are found in the outer areas.

Explanation:

Step1: Recall the relationship between intrinsic luminosity and apparent brightness

Apparent brightness $b$ of a star is related to its intrinsic luminosity $L$ and distance $d$ by the formula $b=\frac{L}{4\pi d^{2}}$. Given that the stars are at the same distance from Earth (same $d$), the star with higher intrinsic luminosity will have higher apparent brightness.

Step2: Compare the intrinsic luminosities

The first star has an intrinsic luminosity of $1.9L_{\text{sun}}$ and the second star has an intrinsic luminosity of $7.3L_{\text{sun}}$. Since $7.3L_{\text{sun}}>1.9L_{\text{sun}}$.

Answer:

The second star will appear brighter.