Calculating the Moment of Inertia of the Sun for Determining Rotational Energy

[AndersLau]

I want to find the rotational energy of the sun.
E_rot=1/2*I*ω²

m=1.9891*10^30 kg
r=6.955*10^5 km


When I am using the formula for a sphere's moment of inertia: I=2/5*m*r²
I'm getting 3.848671797*10⁴⁷ km*m²

Can i find the moment of inertia in another way? the moment of inertia needs to be in *10⁴⁶ , to get the rotational energy right.

Thank you.

 

[D H]

A uniform density sphere is a fairly bad model even for the earth, which is more or less solid. For a gas it is an incredibly lousy model. The sun's core contains about half of the total mass of the sun but only 1.5% of its total volume.

Unless you want to get into astrophysics, you are going to need an empirical value. From http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html, I/MR² for the sun is 0.059. Compare that for a uniform density sphere, where I/MR²=2/5 or 0.4.

 

[AndersLau]

Thank you very much for the answer, that sorts it out. Much appreciated.
I'm waiting with the astrophysics :)