carbon monoxide

1
CO
carbon monoxide first synthesised in the late
18th century common terrestrial molecule
2
CO
first detected in the ISM in 1970 subsequently
isotopologues 13CO, C18O, C17O, 13C18O,
13C17O very stable, very abundant ( 10-5
relative to H2 ) used to measure masses of
molecular clouds and as a tracer of dense gas
3
Dame, Hartmann Thaddeus, ApJ 547, 792 (2001)