Free Astronomy Magazine November-December 2023

11 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING U ndergraduate student Lily Kettler, left, professor Joaquin Vieira and graduate student Kedar Phadke are part of an international team that detected complex organic molecules in a galaxy more than 12 billion light-years from Earth – the most distant galaxy in which these molecules are now known to exist. [Photo by Fred Zwicky] bility and varied chemistry. On Earth, they are most often found in bitumen, a thick, viscous form of pe- troleum, but may be most com- monly associated with the incomplete combustion of organic materials – from raging forest fires to the burning kindling in the fam- ily hearth to the match that can ini- tiate both. They are generally stable molecules and result from reactive carbon atoms and hydrocarbon fragments trying to combine and rearrange into geometries that are stable under harsh conditions, be those fires on Earth or the high-ul- traviolet (UV) conditions around new and old stars. In terms of the detection of any molecules, astronomers and astro- chemists benefit greatly from the general absence of very large mole- cules in space. Just as a conversation is easier with only one person in a room answering your question than with 1,000 people in that same room simultaneously providing dif- ferent answers to that same ques- tion, small molecules absorb and emit photons of a very limited set of energies that are easier to detect when the quantities and variety of other molecules is limited. These en- ergies become the vibrational and electronic spectra from which we obtain what are referred to as spec- tral “fingerprints” – features in these spectra that, with high confi- dence, correspond to very specific arrangements of atoms. Not only is water very different from carbon dioxide or methane, but even dif- ferent arrangements of the same atoms, referred to chemically as structural isomers , produce unique spectra. These fingerprints also seem to hold across space and time. When a mo- lecular spectrum is recorded from a sample brought back from a mole- cule on Ryugu or, eventually, some sample return mission from Mars,