planets of the demigods, but My devotees reach My supreme abode. (Gita, VII:20-23)
In this way, we can go to the sun, the moon, or any other planet. However,  Bhagavad-gita  advises us not to go to any of these material planets, not even the Brahmaloka, which can only be reached by mechanical means after forty thousand years. In the spiritual sky there are innumerable planets which are never annihilated, but there is one called Krsnaloka Vrndavana, which is the supreme planet.
Bhagavad-gita  gives us the opportunity to leave this material world and to go to that eternal existence in the eternal abode of the Lord.
The description of this material world is given in the Fifteenth Chapter of  Bhagavad-gita . The material world is described as an  asvattha  (pipal) tree, which has its roots upward. Do you know of a tree which has its roots upward? We have experience of this if we stand on the bank of a river or reservoir. We can see, in the reflection, that the tree's roots are upward and its branches are downward. So this material world is a reflection of the spiritual world, just as the reflection of the tree from the bank is seen to be upside down. This material world is called shadow. In the shadow there cannot be any substance, yet we can understand from the shadow that there is a substance. In the reflection of the spiritual world there is no happiness, but in the spiritual world itself, there is real happiness.
The Lord suggests that the eternal spiritual world can be reached by one who is  nirmana-mohah  (Gita, XV:5). Let us examine this phrase. We are all after designations. Artificially, we seek designations. Someone wants to become Sir, or Lord, or President, or King, or rich. These designations belong to the body, but we do not. We are not body; we are pure spirit soul. As long as we are attached to such designations, we are associated with the three modes or qualities of material Nature. We must learn to become detached by entering into the service of the Lord. So long as we are not attracted by devotional service to the Lord, then we cannot be detached from the three modes of material Nature. The Lord says that these attachments are due to our lust: We want to be lords over the material Nature. And, as long as we want to lord it over material Nature, there is no chance of going back to the spiritual kingdom of God. That eternal kingdom, which is not destructible like this material world, can be approached only by one who is not bewildered or attracted by this material Nature. One who is attracted by devotional service to the Lord can go to that eternal kingdom.