BMWX1

Questions and Answers

Your Questions About X10

July 26, 2013

Mandy asks…

What is the brightness (B) of polaris, in watts per square meter, as observed from earth?

The north star (Polaris) is 4.1X10^18 meters away from Earth and has a luminosity (L) of 8.7 X10^29 watts. Ignoring the effects of the atmosphere what is the brightness (B) of polaris, in watts per square meter, as observed from earth?

Administrator answers:

OK! This looks like a challenging one, so I am going to have to sharpen my pencil, roll up my sleeves, get my good pair of scissors out (since i like to cut and paste), & put on my hard thinking cap on ;)

concerning a star’s brightness, i normally describe it in terms of magnitude. Nonetheless, apparently ;) it is fairly easy to measure a celestial object’s brightness or its luminosity, as observed from the earth ;) with CCDs and other analytical instrumentations one can find in any astro-laboratory. But let’s pretend just for one moment that those instruments are not available. Based on the data you provided, i can use a well-known relation in order to answer your Q:
Luminosity of Polaris (L) = Apparent brightness of Polaris (B) (4pi) distance of Polaris from earth (D)^2
are you following any of this?
So brightness in terms of Watts per meter squared is 8.7×10^29 W/(12.57)(4.1×10^18 m)^2 or approximately 4.12 nW/ m^2
=P

Powered by Yahoo! Answers

Related posts:

  1. Your Questions About Bmw X 1200
  2. Your Questions About X100
  3. Your Questions About X10
  4. Your Questions About X5 Bmw
  5. Your Questions About X10