The concept, theory and practice of astral projection dates back to ancient times. Historically, the practice of astral travel and projection was limited to society's elite or spiritual hierarchy. Through the years, due to human nature, it has become a widespread phenomenon.
The Aura is believed to be electromagnetic radiation caused by the vibrating energy from within the particles that make up the atoms. The Aura around the human body consists of electromagnetic energy in the form of waves.
The third eye is not really a part of the physical body. It is part of the second body which is etheric body. Your etheric body is a body which is similar to your physical body over which it is superimposed, it has a corresponding spot in the physical body, but it is not part of it, so far the closest reference scientist discovered on psychical body is the Pineal Gland.