The Taurus Molecular Cloud is the dark, obscured region in the upper left of the image, where the gas and dust are blocking the stars behind the cloud from view. Taken from Charlottesville, VA on January 2, 2018. Credit: Brett A. McGuire
For the first time, scientists have identified a complex molecule in a distant part of the solar system, according to research published Thursday in the journal Science. The find brings scientists closer to solving a 30 year old astronomical mystery.
Why it matters: The researchers identified benzonitrile, a molecule made of carbon, hydrogen and nitrogen, which is thought to be a building block for two other types of molecules that are possible precursors for life on Earth. By finding it — and developing a technique precise enough to identify specific molecules in distant space — scientists are closer to understanding the types of material that may form planets and the composition of our universe.
The mystery: 30 years ago, scientists saw bands of infrared light in many places in interstellar space that couldn’t be explained. They suspected large groups of two molecules — polycyclic aromatic nitrogen heterocyles (PANH) and polycyclic aromatic hydrocarbons (PAH) — could be responsible. By one estimate, 20% of the carbon in the universe is bound up in a PAH. On Earth, they’re considered a carcinogen, and are produced when things burn — like fossil fuels.
Both PAH and PANH are potential precursors to life on Earth but are extremely hard to find in interstellar space so researchers instead chose to hunt for its precursor benzonitrile. Identifying it brings them closer to solving that mystery. Additionally, Brett McGuire and his team at the National Radio Astronomy Observatory noted that benzonitrile could, itself, be involved in the creation of the mysterious infrared bands.
"[The molecules] can form the seeds for interstellar dust. This dust eventually forms rings and planets," McGuire said in a press conference. Additionally, they contain carbon and hydrogen, which are essential for life. When exposed to radiation, they could break down to form life's building blocks, said McGuire.
How they did it: The study authors pointed the Green Bank Telescope at a distant molecular cloud in the Taurus region, and precisely measured the wavelengths the telescope absorbed. They were able to identify a number of molecules, including benzonitrile. Then, they performed a series of lab experiments to confirm that benzonitrile does, indeed, produce the wavelengths seen in Taurus.
One cool thing: Aromatic molecules aren’t called that because of what they smell like, but for the type of bonds they form. BUT: for the curious, benzonitrile smells like almonds.