Carbon monoxide (CO) is the most abundant C-bearing molecule in the universe.
It is the
second most common molecule in dense interstellar clouds, after H2. It is
found in comets and
the atmospheres of several planets. It has
also been detected in brown dwarfs such as
Gliese 229b and
Epsilon Indi B.
Since 1952, it has been known that
CO is present in the atmosphere of our own sun, residing in the
chromosphere. At least four of the
isotopomers have been detected
CO and some of its isotopomers have also been
detected in protoplanetary disks.
CO is observed in the interstellar media by means of its characteristic
It is used as a tracer
for detecting molecular hydrogen and is consequently used extensively for mapping
molecular clouds in
our own galaxy and in
sources, where its 13CO, C17O, and C18O isotopomers have also been detected.