Answer to Question #108030 in Astronomy | Astrophysics for Priya jaiswal

Question

A white drawf star has a mass 10^30 kg. It's luminosity is 10^24j/s. Calculate how long it can survive with its present luminosity if it's internal temperature is 10^7k .

Answer 1

The mass measured in solar masses:

$$M=0.5M_☉.$$

The luminosity measured in solar luminosities:

$$L=\frac{10^{24}}{3.828\cdot10^{26}}L_☉=0.0026L_☉.$$

The lifetime measured in solar lifetimes is:

$$t=\frac{M}{L}=\frac{0.5M_☉}{0.0026L_☉}=192t_☉,$$

or

$$t=1.92\cdot10^{12}\text{ years}.$$