Applying Colour Gradient to Radiating Lines

Hi,

Was trying to apply colour to radiating lines but want to give the illusion that the centre is made up of a orange sphere and as the lines go further away from the centre they turn yellow and eventually white. So it should look like an orange sphere in the centre with and yellow sphere around it. Not sure if that's clear. Have attached what I have done so far. 

Basically the colour needs to get lighter (from orange to yellow to white) as it gets further from the centre).

Thanks