Planet gravity help need guidance no code

I need to implement a gravity system where some gameobjects are attracted to other gameobjects but not going to the surface and sticking to it.

I just need and guidance and precious words from all of you ( well source code helps ) but explanation and technique is appreciated :)

Only reason I am posting here is because unity answer is faster then unity forums, I had to wait weeks to get answer in forum :(

I am completely blank about this

Thank you :)