Comet 2I/Borisov Has an Unusual Composition
Interstellar comet 2I/Borisov, a mysterious visitor from the depths of space, is the first conclusively identified comet from another star. The comet consists of a loose agglomeration of ices and dust particles, and is likely no more than 3,200 feet across, about the length of nine football fields. ALMA observed hydrogen cyanide gas (HCN) and carbon monoxide gas (CO) ejected out of the comet as it approached the Sun and heated up. The ALMA images show that the comet contains an unusually large amount of CO gas. ALMA is the first telescope to measure the gases originating directly from the nucleus of an object that travelled to us from another planetary system.