Chrysophyllum cainito - Star Apple

Thanks for this photo.
I've found a bit more detail about this tree:

Round, baseball sized fruit that when cut has a core that takes on a star shape. Pulp is soft and sweet. The star apple usually comes in two forms, either the dark purple skinned variety with red-purple pulp, or the green skinned variety with clear-white pulp. The star apple is a very popular fruit in many tropical parts of the world.

Thanks, Terratoonie for posting this information. I did forget to mention why it is called Star Apple.

I'll have to post some other pictures of this tree soon. It is not easy to take pictures of trees on private property, however, The San Diego Zoo has many of these trees. This picture was taken at Quail Botanical Gardens.
They have an extensive tropical fruit section just like the San Diego Zoo.