In a cloud where massive stars are being born, there is a hot, dense core. Like a crowded kitchen where the heat of the stove makes smells evaporate, here the warmth from young stars evaporates molecules from the surface of cosmic dust grains. Astronomers pointed the large ALMA antenna array in Chile's Atacama Desert at such a core — G358.93-0.03 MM1—and for the first time caught the radio signal of formic acid.
Formic acid is a simple substance that we also have on Earth: ants secrete it for defense. In space, it is important as a stepping stone to glycine — the simplest amino acid, from which proteins are built. The scientists measured how much acid is in the core: about 2.6 molecules per billion hydrogen molecules. It seems like a small amount, but for the interstellar medium it is a noticeable quantity. The gas temperature there is about 120 degrees above absolute zero (approximately -153°C), like a frosty Antarctic night.
The computer model computed by the authors reproduced the observed amount of acid almost perfectly — a discrepancy of only 11%. This means that chemists correctly understand the path from simple particles to more complex molecules in clouds where stars ignite. Such research is like reading the Universe's cookbook: we see the finished dish (the gas in the core), and models help reconstruct the recipe.
Formic acid was first found in space back in 1970, but in a hot molecular core only now. These cores are considered "factories" of complex organic molecules.
In Carl Sagan's novel "Contact," a radio signal from space contains a blueprint for a machine, but in reality radio telescopes catch signals from simple molecules, like formic acid, which could become part of life.