An astronomer observes two Type Ia supernovas in different galaxies.The first is in a galaxy 100 Mpc away.If the second supernova is 10⁶ times fainter than the first but has an identical light curve,how far away is the second supernova's host galaxy? A) 10³ Mpc B) 10⁸ Mpc C) 10⁶ Mpc D) 10⁵ Mpc

Question

Quizplus · Accepted Answer

The brightness of an astronomical object decreases with the square of the distance. If the second supernova is $10^6$ times fainter, it means it is $\sqrt{10^6} = 10^3$ times further away. Therefore, if the first galaxy is 100 Mpc away, the second is $100 \times 10^3 = 10^5$ Mpc away.

An Astronomer Observes Two Type Ia Supernovas in Different Galaxies