Create an empty icon with 64x64 pixels. Draw a filled circle with center 32,32 and
diameter 55. (pic. 1)
Mark a color region from black to red and choose 'radial filling' in the gradation
options. Now choose the 'Fill' tool and click in the circle at about 45,45. (pic.2)
Now choose 'Antialiasing' with the value '10'. (pic. 3)
Resize the icon to 32x32 pixels. Answer the question 'Do you want to
resize the contents of the current icon to the new size?' with 'YES'.
To make the sphere more realistic you can add a highligth. To do this
change the current drawing color to white and click on the button
'Highlight'. In the appearing dialog click one on the arrow pointing to the
right bottom the change the position to 6, 6. Change the size to 5 and the
intensity to 7. Click on OK and the sphere should look like the one in
picture 5.