The Cosmic Man, or Celestial Man, is found in many religious and spiritual teachings including the Hermetic, the Gnostic and the Cabbalistic Jewish.   The cosmic man is the archetype of the ideal man - man as he existed before the fall - but is also the goal of spiritual teachings, to become that highly evolved spiritual being, full enlightened, fully aware, free from death, disease, and attachment to material things.  In the many ancient traditions, while some details vary, essentially the cosmic man is the same.  In alchemy, this ideal man was known as Phos, which is Greek for both man and Light depending on how you pronounce it.  This is no accident because cosmic man is always associated with light, specifically, Divine Light or Spiritual Light.  Hermetic writings say that Eternity is an image of God, Cosmos in an image of Eternity, The Spiritual Sun is an image of Cosmos, and man is an image os the Spiritual Sun.  In the Cabbala, he is Ayn-Sof or Adam Kadmon, the first man, the original man.  In most of these schools, one of the things students should do to become spiritually enlightened is to make contact with that ancient archetype that dwells in each of us and learn from it.
    Unfortunately, today both Cosmic Man and Celestial Man are names of comic book characters.  I have never read these comics, but I think it is fairly safe to say that those characters are somewhat different from the original meaning of the names as used in spiritual and religious schools.