29:50 Modern Astronomy
Fall 2002
Lecture 17 ...October 14, 2002
Molecular Clouds as Molecular Reactors
(1) What kind of molecules do we find? Simple ones to start with: carbon monoxide (CO),
water (H 
O), and ammonia (NH 
). However, and surprisingly, we also find very complex
ones: Formaldehyde (H CO), Formic acid (HCOOH), and ethyl alcohol (CH CH OH).
(2) 
Table with molecules discovered to date in space.
Summary of characteristics. (A) Molecules include multi-atomic ones. (B) Most of them
are organic. In the latter, the simplest amino acid has been found in space.
(3) We are certainly just seeing the tip of the iceberg. When we look at a molecular
cloud like Orion, there are many unidentified spectral lines which must come from even
more complicated molecules than we have discovered so far.
URL of the millimeter spectrum of Orion.
(4) Some of these complex molecules probably include the polycyclic aromatic hydrocarbons,
of PAHs.
(5) All of this leads to the speculation that life may have began out among the stars.
The gas from which the Earth and other solar system objects formed was full of complex organic
molecules. This material could well have, and probably did, supply the building blocks for
life. URL for carbonaceous chrondite meteorites.
