For the first time, astronomers have detected essential components of life frozen in ice beyond our galaxy. Researchers exploring the Large Magellanic Cloud identified a range of complex organic molecules encased in ice orbiting a young star. Among these findings were ethanol, acetaldehyde, and methyl formate, compounds never previously observed in ice outside the Milky Way. Additionally, acetic acid was detected in its frozen form for the first time in space.
The study, led by astrophysicist Marta Sewiło from NASA“s Goddard Space Flight Center and the University of Maryland, indicates that the building blocks necessary for the chemistry of life are not confined to our galaxy, but are likely prevalent throughout the universe. “With this discovery,” Sewiło noted, “we”ve made significant advancements in understanding how complex chemistry emerges in the Universe and opening new possibilities for research into how life came to be.”
In astrophysics, complex organic molecules (COMs) refer to substances consisting of at least six atoms, including at least one carbon atom. This category covers molecules such as ethanol (CH3CH2OH), methyl formate (HCOOCH3), and acetaldehyde (CH3CHO), as well as larger compounds like iso-propyl cyanide ((CH3)2CHCN). These molecules are crucial for scientists because they serve as chemical precursors to vital biological structures, including amino acids, sugars, and nucleobases. Their presence in space enhances our understanding of prebiotic chemistry and the environments where these precursor compounds may have originated long before Earth existed.
The Large Magellanic Cloud (LMC) presents a distinct environment compared to the Milky Way, characterized by a lower abundance of heavy metals—including elements heavier than helium like oxygen, carbon, and silicon. Moreover, the LMC has significantly less dust to obstruct light and exhibits vigorous star formation that bathes the galaxy in ultraviolet radiation. This raises intriguing questions about the formation of COMs in the LMC.
A young star known as ST6, located approximately 160,000 light-years from Earth within a superbubble called N158, was the focus of this research. This region is in proximity to the well-known star-forming area known as the Tarantula Nebula. Utilizing the James Webb Space Telescope (JWST), Sewiło and her team captured mid-infrared light from the icy material surrounding ST6 to examine the chemical processes occurring there. They compared the spectra collected to a database of known COM signatures, confirming the presence of methanol, acetaldehyde, ethanol, methyl formate, and acetic acid.
Prior to this study, acetic acid had only been detected in space as a vapor. Its discovery in a frozen state corroborates theoretical models and laboratory experiments suggesting that it plays a role in reactions on grain surfaces that lead to the formation of prebiotic compounds in space. The presence of these molecules provides compelling evidence that they result from grain-surface chemistry, where ice develops on dust grains, creating thin layers that facilitate reactions among the molecules.
Remarkably, this process appears to occur even in the metal-poor and radiation-rich conditions of the LMC. The research team intends to broaden their investigation to include additional young stars within the LMC to ascertain whether similar chemical processes are prevalent throughout the entire dwarf galaxy or if ST6 presents a unique case. “Currently, we have only one source in the Large Magellanic Cloud and just four sources with detected complex organic molecules in ices in the Milky Way,” Sewiło stated. “We require larger samples from both galaxies to confirm our initial findings, which indicate variations in COM abundances between these two galaxies.”
This pivotal research has been published in The Astrophysical Journal Letters.
