Astronomers, among them Yuxin Lin and his collaborators, have identified methanimine in the L1544 cloud, located 554 light-years away. This molecule, composed of carbon, hydrogen, and nitrogen, represents a step towards more elaborate compounds like amino acids. Its presence in this cloud, which is not yet a star, reveals that active chemical reactions are already setting the stage for future organic chemistry.
Belonging to the vast Taurus molecular cloud, a region conducive to stellar births, L1544 has a calm character. Matter falls slowly toward its dense center, a tranquility that allows molecules like methanimine to form in the warmer outer layers before diffusing throughout the cloud, and this, even before its collapse into a star.
An infrared view of the Taurus molecular cloud, where the L1544 cloud is visible as a bright spot at the bottom left. The latter is a pre-stellar core, awaiting stellar formation.
Credit: ESA/Herschel/SPIRE The genesis of methanimine primarily occurs in the less dense areas of the cloud, where temperatures are a bit higher. As matter flows toward the center, this molecule accompanies the movement, depositing in various regions. It could thus survive until the star's birth and become integrated into the material disk.
When planets begin to assemble from this disk, they could inherit prebiotic molecules like methanimine. Consequently, some future planets might have from their origin the basic building blocks necessary for the emergence of life, if conditions are favorable.
The researchers published their results in
The Astrophysical Journal Letters, demonstrating that this chemistry occurs even during the cold and calm phases. This work presents one way in which planetary systems acquire their initial organic compounds, long before any life could emerge.
By detailing these mechanisms, scientists aim to better understand the potential origins of life in the galaxy. Future observations could uncover other similar molecules in other clouds.
A wide view of the Taurus molecular cloud, where L1544 is located. Its relative proximity makes it an ideal place to study star formation.
Credit: Digitized Sky Survey 2. Acknowledgment: Davide De Martin Pre-stellar cores
Pre-stellar cores are dense clumps of gas and dust in space, which are at an intermediate stage before collapsing to form stars. They contain all the matter necessary for creating a stellar system but remain relatively stable until gravity becomes too strong. This process can take thousands or millions of years, during which temperature and density gradually increase.
When gravity prevails, the core collapses on itself, triggering the formation of a protostar. This phase is marked by heating and increased activity, contrasting with the initial calm. Cores like L1544 are therefore natural laboratories for studying the earliest stages of star and planet birth.
The structure of these cores features a dense, cold center, surrounded by warmer outer layers. This configuration allows chemical reactions to occur at different temperatures, influencing the composition of future systems. By observing these regions, astronomers can trace how elements combine even before stellar ignition.