A cepheid variable in a nearby galaxy looks "10^6" times fainter than an identical Cepheid in the Milky Way? The Cepheid in the Milky Way is 1000 parsecs away. How far away is the nearby galaxy?
1 Answer
Mar 27, 2016
Explanation:
The absolute brightness (i.e. number of photons per unit time for a fixed size detector) decreases as the square of the distance.
To prove this for yourself, think of the photons passing through the surface of a sphere of radius
So if the absolute brightness decreases by a factor of
That makes the distant cepheid variable