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## Homework Statement

Calculate the radius of a 1.3 M

_{sun}white dwarf using the mass-radius relation for white dwarfs. Give the answer in solar radius.

## Homework Equations

Mass-radius relation: $$R \propto M^{-\frac{1}{3}}$$

## The Attempt at a Solution

So I've tried the following:

$$R_{D} \propto M_{D}^{-\frac{1}{3}} \Rightarrow \frac {R_{D}} {R_{sun}} = \frac{M_{D}^{-\frac{1}{3}}} {M_{sun}^{-\frac{1}{3}}} \Rightarrow R_{D} = \frac{M_{D}^{-\frac{1}{3}}} {M_{sun}^{-\frac{1}{3}}} R_{sun}$$

$$ \Rightarrow R_{D} = \left( {\frac {1.3 M_{sun}} {M_{sun}}} \right) ^{-\frac{1}{3}} R_{sun} = \left( 1.3 \right) ^{-\frac{1}{3}} R_{sun} $$

This gives me an answer of about ##0.916~{R_{sun}}## , which is incorrect. Where am I going wrong here?

Thanks in advance for any help.