help with gravitational fields

[log1c]

A planet is revolving around a star 2.9 X 10^7 km away, how long does it take to go around oncee?

also
what is the ratio of a p+ gravitational field to that of an -e?

[Sirus]

For the first question: http://www.physicsforums.com/showthread.php?t=51690&highlight=orbital+period. You need the mass of the star.

Second question: use your formulas for gravitational field; should be the ratio between the masses of the two particles, since everything else is constant.