Suppose a star has the same luminosity as our sun (3.8×1026watts) but is located at a distance of 10 light−years . what is its apparent brightness?

One light year is equal to 9.46*10^15 m. The star is 10 light years away, which is the same as 9.46*10^16 meters. The equation that relates brightness to distance and luminosity (in watts) is brightness = Luminosity/(4*pi*distance^2). The sun has a luminosity of 3.8*10^26 watts (NOT 3.8*1026 watts, as indicated in the problem statement). Using the given distance with the actual implied luminosity of the star: Brightness = 2.8*10^26/(4*3.14159*(9.46*10^16)^2) = 2.49 e-9 W/m^2

Master planned communities outside of chicago. note: population density means people living in an area per square mile. chicago, an urban and highly populated area has a much more higher density than a desert, amish community, settlement, or nomadic region.