If a contracting prostar is 3 times the radius of the sun and has a temperature of 1680 k how lumminous will it be relative to the sun? Use luminosity radius temperature to the relation. The surface temperature of the sun is 5800k

If a contracting protostar is two times the radius of the Sun and has a temperature of only 1890 K, how luminous will it be relative to the Sun?

A red giant star has a temperature of 3900  K and a luminosity of 13600 LSun. How many times bigger is this star than the Sun? Hint: You need the surface temperature of the sun for this problem. Use the value in the book, 5800K.

A certain star has a temperature twice that of the Sun and a luminosity 64 times greater than the solar value. What is its radius, in solar units?

How is the blue color of a reflection nebula related to the blue color of the daytime sky?

If the sun expanded to a radius 200 times it's present radius, what would the average density be (in g/cm^3?)

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A star with spectral type A0 has a surface temperature of 9600 K and a radius of 2.2 RSun. How many times more luminous is this star than the Sun? (if it is less luminous enter a number less than one) 36.854 This star has a mass of 3.3 MSun. Using the simple approximation that we made in class, what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr.

(Answer don't copy with hand written please)As a star runs out of hydrogen to fuel nuclear fusion in its core, changes within the star usually cause it to leave the main sequence, expanding and cooling as it does so. Would a star with a radius 12 times that of the Sun, but a surface temperature 0.5 times that of the Sun, be more, or less luminous than the Sun? Show and explain your reasoning. You may assume the surface area of a sphere is A = 4πr2.