Understanding solar system formation is one of the most complex problems of interest today, and it requires understanding so much more than just a star and its worlds: it requires understanding the evolution of our universe. Worlds like our own require the clouds of dust and gas our solar system once was to contain all the chemistry required for life. As we’ve often talked about, the universe started out with only hydrogen, helium, and trace amounts of lithium and beryllium. It is through complex nucleosynthesis in stars and in the environments of explosively dying and merging stars, that everything else is formed. That gold you wear? That probably came from a neutron star merger. The platinum inside your cell phone? It may have originated in a supernova. Even the carbon that makes up so much of our body came from regular stars undergoing nuclear reactions in their cores. 

While astronomers have long understood the need for heavy elements to form to get planets and subsequently life, the history of complex molecules needed for life has remained more mysterious, with folks working to create necessary molecules in labs that simulate the conditions on a young planet, and astronomers looking at the material between the stars to see what already exists. Now, in a new paper in the Astrophysical Journal, we learn that methanol and acetaldehyde exist in molecular clouds in regions where stars have not yet started to form. 

Thirty-one dense regions, called starless cores, were observed, and all thirty-one had methanol while seventy percent contained acetaldehyde. Some of these cores may someday collapse to form stars, but their fate isn’t set and this research tells us what systems look like before solar system formation really gets started. According to study co-author Yancy Shirley, “This tells us that the basic organic chemistry needed for life is present in the raw gas prior to the formation of stars and planets.” What chemistry led to the formation of these organic compounds is unknown. 

According to lead author Samantha Scibelli: Inside these cores, which we think of as birthplaces, cocoons, and nurseries of low-mass stars similar to our sun, the conditions are such that it’s hard to even create these molecules. By doing surveys like this, we can understand better how precursors to life come into existence, how they migrate and enter solar systems at later stages of star formation.

While this research still doesn’t tell us how these molecules form, it does tell us they don’t need to form during solar system formation, essentially kicking the problem back in time. It also helps us understand just what the birthplace of our solar system could have looked like. Scibelli explains it as follows: Our solar system was born in a cloud like this, but the cloud is not there anymore for us to see. Looking at objects in space is a bit like looking at a photo album with snapshots taken of different people at different stages of life, from their baby days all the way to old age, and in our case, starless cores serve as stellar sonograms.

More Information

The University of Arizona news release 

 “Prevalence of Complex Organic Molecules in Starless and Prestellar Cores within the Taurus Molecular Cloud,” Samantha Scibelli & Yancy Shirley, 2020 March 5, Astrophysical Journal (Preprint on arxiv.org)