3I/ATLAS: Initial observations suggest a nucleus size ranging from 0.32 to 5.6 kilometers, with a most likely diameter under 1 kilometer. The comet’s coma, a cloud of gas and dust, is composed of carbon dioxide, water vapour, carbon monoxide, and carbonyl sulfide. Notably, it emits atomic nickel vapour and cyanide gas, a first for interstellar comets.
2I/Borisov: Borisov was the first interstellar comet. Estimated nucleus size between 0.4 and 0.5 kilometers. Its coma contains water vapour, carbon monoxide, and other typical cometary compounds. A significant discovery was the detection of atomic nickel vapour in its coma, observed at a distance of 2.322 AU from the Sun.