# Astronomy

posted by .

I have two stars A = 7150K and B = 4850K.A is 20 times brighter than B.
Assuming L/Lv is the same for both stars find the ratio ofthe radii of A and B.
I have the equation R/R= (L/L)^1/2(T/T)^2.
I can do this for each star in terms of solar masses but i am unsure which temperature goes in the numerator/denominator?
Is (L/Lv)^1/2 sqr root 20?

• Astronomy -

luminosity is proportional to r^2*temp^4
so if are comparing r, then

r^2 prop Luminosity/T^4

so in your

Ra/Rb= sqrtLa/Lb) * (tb/ta)^2
= sqrt (20) * (4850/7150)^2

## Similar Questions

1. ### Physics

In a binary star system, two stars orbit about their common center of mass, as shown in the figure . If r2 = 2r1, what is the ratio of the masses m2/m1 of the two stars?
2. ### astronomy

Suppose the distance between two stars doubled while the mass of each star doubled as well. What would happen to the orbital period of the two stars?
3. ### Science need help

Astronomers believe that the biggest stars in the Galaxy may be a hundred times more massive than the Sun, but are a million times brighter. Would you expect such stars to have longer, shorter or comparable lifetimes to that of the …
4. ### physics

mc030-1.jpg Two stars are bound together by gravity. The larger star has four times the mass of the smaller star. Which diagram best illustrates the orbital motion of the two stars?
5. ### maTH

I NEED HELP REALLY BAD 5. Directions: Select all the correct answers. Nancy is studying constellations in science class. Two things are strongly supported by all random samples of the number of stars in a constellation. Most constellations …
6. ### science

Why can certain stars sometimes be identified as eclipsing binary stars?
7. ### Physics

two stars with equal mass of 4.0x10^15 kg are separated by a distance of 2 km. They are moving in circular obits around the middle between the two stars. What is the speed of the stars?
8. ### Physics

Two equal-mass stars orbit their centre of mass. The distance between the stars (measured from the centre of mass of each) is 1 AU. What is the period of revolution in years?
9. ### science help

An astronomer sees two stars in the sky. Both stars are equally far from Earth, but the first star is brighter than the second star. Which of the following is a valid conclusion about the first star?
10. ### physics

Two stars with masses 2.75 x 10^30 kg and 5.92 x 10^30 kg form a binary system. If the two stars have an average separation of 7.28×10^8 km, compute the magnitude of the gravitational force in Newtons between the stars. Express your …

More Similar Questions