Thanks for this interesting question…

Heaven is usually thought of as our final destination after we die, and it is the ideal of perfection where we will have no more sorrow, no more pain, and we will be with God.

The Urantia Book gives us a greatly enlarged revelation of the worlds on high—worlds that we will visit on our eternal voyage. Some of these, the authors tell us, are places that will truly fit humanity’s ideas of what “heaven” is really like.

For example, we learn that:

Jerusem, the headquarters of your local system of Satania, has its seven worlds of transition culture, each of which is encircled by seven satellites, among which are the seven mansion worlds of morontia detention, man’s first postmortal residence. As the term heaven has been used on Urantia, it has sometimes meant these seven mansion worlds, the first mansion world being denominated the first heaven, and so on to the seventh. Jerusem, the headquarters of your local system of Satania, has its seven worlds of transition culture, each of which is encircled by seven satellites, among which are the seven mansion worlds of morontia detention, man’s first postmortal residence. As the term heaven has been used on Urantia, it has sometimes meant these seven mansion worlds, the first mansion world being denominated the first heaven, and so on to the seventh. (15:7.5)

…the system headquarters [of Jerusem] is truly the heaven visualized by the majority of twentieth-century religious believers. (46:0.1)

You should consider the statement about “heaven” and the “heaven of heavens.” The heaven conceived by most of your prophets was the first of the mansion worlds of the local system. (48:6.23)

In this sense, then, “heaven” can surely be thought of as being an actual planet. These worlds referenced above are what is termed “architectural worlds, ” or, worlds “which are built according to plans and specifications for some special purpose, ” but they are planets nonetheless. Please click on any of the links above to open the quotes, so you can read more about “heaven.”

I hope this answer has been helpful to you.