Diatomic carbon (systematically named ethenediylidene and dicarbon(C—C)), also called dicarbon, is an inorganic chemical with the chemical formula C=C (also written [C
2] or C
2). It is a gas that only exists above 3,642 °C (6,588 °F)), below which it aggregates into graphite or fullerenes. It occurs in carbon vapor, for example in electric arcs; in comets, stellar atmospheres and the interstellar medium; and in blue hydrocarbon flames.