Solar Fingerprints: How we observe the Sun’s features and regions There's more to the Sun than meets the eye. Every object in the universe that emits EM radiation has its own unique spectrum, like a fingerprint. The physical properties of each of the Sun's regions (like temperature) determine the nature of its spectrum. For example, the Sun's Core only produces very high energy gamma radiation, a product of nuclear fusion, while the Photosphere produces visible light. The EM Spectrum All light travels as waves. The wavelength can be long such as radio waves or extremely short such as X-rays or gamma rays. Most of the EM spectrum is invisible to us but we can detect its presence using special instruments.