There are no races of intelligent creatures in other galaxies. The idea that there are would be the heresy of antipodeanism.
God could have created such a race and interacted with them, but he did not.
God only reveled to us what we Humans need for salvation. God did not publicly revel the true nature of Heaven, the universe, etc. to us. However, He does slowly revel these truths to us as we grow in wisdom and knowledge; when we are ready for the next bit of truth.
Jesus is the only “fully human, fully God” Son of God. Jesus Christ is the Son of Man. Perhaps there are multiple Heaven’s, one for each species in the universe. Or perhaps the 2nd Person in the Trinity was incarnated on every planet which had original sin? Perhaps on some planets the devil wins and on others 2nd Person wins?
On Vulcan, the 2nd Person of the Trinity would be “fully Vulcan and fully God,” but would not share in the human nature of Christ. His nature would be fully alien and fully God; but still God. In a way (IF GOD WANTED TO DO THIS), the 2nd Person of the Trinity could have been Incarnated and died on millions of different worlds, for millions of different creations.
Considering the idea that aliens might exist isn’t heresy. Heresy would be thinking that the existence of aliens negates or somehow invalidates the Church.
God is not limited, only we are.
The universe can be teaming with life, or we might be it. Either way, it’s God’s will. And either way, we will NEVER know for sure until/if we meet an alien. No matter what we think, we are not God. And the scriptures do not address the subject one way or another. The scriptures are only focused on Human salvation.
Personally, I just think since God is Love, and since creation was an act of Love by God, that He would want to keep creating life due to His infinite love. Even the Vatican has studied the theological impactions and questions of extraterrestrial life.
One Catholic priest was even ask if he would baptize an alien, and the priest replied with “yes, if he/she asked me to.”
What’s truly awesome about being Catholic is that no matter what happens in science, every discovery we make only further illustrates the Awesome Power of God. Our Faith and science will never truly be in conflict because The Truth is God’s Truth.