Question

After the sun exhausts its nuclear fuel, its ultimate fate may be to collapse to a white dwarf state. in this state, it would have approximately the same mass as it has now, but its radius would be equal to the radius of the earth. (a) calculate the average density of the white dwarf.

Answer 1

To calculate the density of the white dwarf we need the mass of the Sun and the radius of the Earth:
- Sun mass:
`M=1.99 \cdot 10^(30)kg`
- Earth radius:
`r=6.37 \cdot 10^6 m`
Assuuming the dwarf to be a perfect sphere, its volume is
`V= (4)/(3) \pi r^3`.
The average density is given by

`d= (M)/(V)`
so, substituting we find

`d= (M)/( (4)/(3)\pi r^3 )=1.83 \cdot 10^9 kg/m^3`