Question

Distances to very remote galaxies are estimated based on their apparent type, which indicates the number of stars in the galaxy, and their measured brightness. Explain how the measured brightness would vary with distance. Would there be any correction necessary to compensate for the red shift of the galaxy (all distant galaxies have significant red shifts)? Discuss possible causes of uncertainties in these measurements.

a) Measured brightness decreases with distance; no correction needed
b) Measured brightness increases with distance; correction needed for red shift
c) Measured brightness remains constant with distance; correction needed for red shift
d) Measured brightness has an inverse relation to distance; no correction needed

Answer 1

The measured brightness of a galaxy decreases with distance due to the inverse square law of light. A correction is necessary to compensate for the red shift of the galaxy. Possible causes of uncertainties in these measurements include interstellar dust, stellar variability, instrumental errors, and atmospheric conditions. a) Measured brightness decreases with distance; no correction needed is correct answer.

Step-by-step explanation:

The measured brightness of a galaxy would vary with distance due to the inverse square law of light. As the distance to a galaxy increases, the measured brightness decreases. This is because the same amount of light is spread out over a larger area, resulting in a lower apparent brightness.

To compensate for the red shift of the galaxy, a correction is necessary. Red shift is caused by the expansion of the universe and causes the light from distant galaxies to be shifted towards longer wavelengths. By correcting for the red shift, astronomers can determine the true brightness of the galaxy.

There are several possible causes of uncertainties in these measurements. One cause is the presence of interstellar dust, which can absorb or scatter light and affect the measured brightness.

Another cause is the variability of stars within a galaxy, which can introduce inconsistencies in the measurement. Additionally, instrumental errors and atmospheric conditions can also contribute to uncertainties in the measured brightness of distant galaxies.