"The Little Prince", by Antoine de Saint-Exupéry. I recommend you read it, if you are unfamiliar with it.

[His tone here is halfway between kindly serviceable and "how come you didn't already know this?". After all, there's always the possibility that this person may not be an earthling, either.]

I believe I forgot to introduce myself. My name is Gorthan, and I am a scientist. As you may have guessed, the stars are my original home.

[While he does not usually tell strangers about his original self, this is vague enough to be acceptable.]