Iron Ions (Fe XII) in the Sun's Atmosphere
Iron exists in small amounts in the solar atmosphere. Since atoms in the Sun's atmosphere are extremely hot, they move around very, very quickly. The atoms often collide, and such collisions can knock electrons loose from an atom. Atoms with missing (or extra!) electrons are called ions. An iron (chemical element symbol Fe) atom that is missing one electron is called Fe II. Normal, neutral iron with a full compliment of 26 electrons is called Fe I.
Under conditions (temperatures around 1,500,000 kelvins) that exist in the Sun's corona (upper atmosphere), an iron atom loses 11 electrons and becomes an Fe XII ion. These ions emit extreme ultraviolet (EUV) radiation at a wavelength of 19.5 nm (195 Å). Radiation at this wavelength allows scientists to see structures and processes at a certain height in the solar atmosphere. These high energy UV emissions are (thankfully!) blocked by Earth's atmosphere, so scientists must use orbiting solar telescopes on satellites above the atmosphere to view the Sun at this wavelength.
On Earth, iron is a silvery-white metal that is found throughout the Earth's crust. It is also a critical component of the human body found in blood cells and necessary for the proper functioning of cells and muscles.