# Homework Help: Density of the sun as a white dwarf.

1. Jul 7, 2009

### Bottomsouth

1. The problem statement, all variables and given/known data

In about 5 billion years, at the end of its lifetime, our sun will end up as a white dwarf, having about the same mass as it does now, but reduced to about 15,000 km in diameter.What will be its density at that stage?

g/cm^3

2. Relevant equations

D=m/v
4/3(3.14)r^3

3. The attempt at a solution

Sun's mass is Sun's mass is = 1.99 x 10^30 kg
kg to g = 1.99 x 10^33
v = 7500 km to 750,000,000 centimeter

D = 1.99 x 10^33 / (4/3)(3.14)(7.5 x 10^33)^3 = 1.12 x 10^54 ???

Is this correct? I have been getting it wrong each time I input the answer

2. Jul 7, 2009

3. Jul 7, 2009

### Bottomsouth

D = 1.99 x 10^33 / (4/3)(3.14)(7.5 x 10^9)^3 = 2.09 x 10^11?

4. Jul 7, 2009

### negitron

You're off by a factor of 10 somewhere. Careful of your exponents.

5. Jul 7, 2009

### Bottomsouth

D = 1.99 x 10^33 / (4/3)(3.14)(7.5 x 10^8)^3 = 6.338 x 10^23
Seems to be wrong.

6. Jul 7, 2009

### negitron

Your equation is correct. Take it one step at a time.

7. Jul 8, 2009

### Redbelly98

Staff Emeritus
Agreed. What is the volume? Then take the ratio mass/volume.