An Etymological Dictionary of Astronomy and Astrophysics

An → emission line in the spectrum of the
→ solar corona caused by highly ionized metal ions; especially those of iron, such as the red and green lines at 6375 Å and 5303 Å [Fe X] (Fe⁹⁺ ion) and [Fe XIV] (Fe¹³⁺ ion), respectively. From their discovery in 1870 until 1939, it was believed that these → forbidden lines would be due to an unknown element, called → coronium. Ultraviolet and X-ray coronal lines are also detectable in stars.

See also: → coronal; → line.