A blue supergiant star has a radius of 7.4 x 1010 m. The spherical surface behaves like a blackbody radiator. If the blue supergiant star radiates an energy rate of 1.29 × 1033 w, what would be its surface temperature (in °C)? The Stefan-Boltzmann constant is 5.67 x 10-8 w/(m2 · K4).

Sirius B is a white star that has a surface temperature (in kelvins) that is four times that of our sun. Sirius B radiates only 0.040 times the power radiated by the sun. Our sun has a radius of 6.96 × 108 m. Assuming that Sirius B has the same emissivity as the sun, find the radius of Sirius B. RSB= O

The next four questions use this description.  Our Sun has a peak emission wavelength of about 500 nm and a radius of about 700,000 km. Your dark-adapted eye has a pupil diameter of about 7 mm and can detect light intensity down to about 1.5 x 10-11 W/m2.  Assume the emissivity of the Sun is equal to 1. First, given these numbers, what is the surface temperature of the Sun in Kelvin to 3 significant digits? What is the power output of the Sun in moles of watts?  (in other words, take the number of watts and divide it by Avogadro's number) Assuming that all of the Sun's power is given off as 500 nm photons*, how many photons are given off by the Sun every second? Report your answer to the nearest power of 10 (e.g. if you got 7 x 1024, give your answer as 25).

#19.13 FIND THE GIVEN, REQUIRED, SOLUTION AND EXPLAIN PER STEPS

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As radioactive plutonium isotopes decay, they generate heat as a byproduct. Pu-239 generates 1.9W/kg of heat. How much heat will 1.25molof Pu-239 release after decaying for three hours? Express this quantity in units of calories. Assume Pu-239 has a molecular weight of 244g/mol.

The radiant flux at Earth is 1365 W/m2. Say we move towards the sun to a radius that is 1/3 the radius of the Earth's orbit. By what factor would the radiant flux increase or decrease?