Much of the carbon in space is believed to be in the form of large molecules known as polycyclic aromatic hydrocarbons, or PAHs. There has been evidence since the 1980s that these molecules are abundant in space, but they have not been observed directly. Now a team of US National Science Foundation-Funded researchers led by Massachusetts Institute of Technology scientist Brett McGuire have identified two distinctive PAHs in a room called the Taurus Molecular Cloud.
It was believed that PAHs only form efficiently at high temperatures – on earth they are by-products of fossil fuel combustion and are found in characters on grilled foods. The Taurus Molecular Cloud has not yet started to form stars, however, and its temperature is about 10 degrees above absolute zero.
This discovery suggests that these molecules can form at much lower temperatures than expected, and it could lead scientists to rethink their assumptions about the role of PAH chemistry in the formation of stars and planets.
“What makes the evidence so important is that not only have we confirmed a hypothesis that has been around for 30 years, but we can now look at all the other molecules in that one source and ask how they react to form the PAHs that we form. We see how the PAHs can react with other things to potentially form larger molecules, and what impact this can have on our understanding of the role of very large carbon molecules in the formation of planets and stars, ”says McGuire, a senior author of the new study that appears in science.
Carbon plays a vital role in the formation of planets. The suggestion that PAHs could also be present in starless, cold regions of space could lead scientists to rethink their theories about what chemicals are available during planet formation. When PAHs react with other molecules, they can form interstellar dust grains, the seeds of asteroids and planets.
"We need to completely rethink our models of how chemistry evolves from starless nuclei to take into account the fact that they make up these large aromatic molecules," says McGuire.
Glen Langston, Program Director in the NSF's Department of Astronomical Sciences added, “As a prime example of the importance of interdisciplinary collaboration and basic research, these researchers have cleverly applied data stacking techniques from the fields of astronomy, chemistry and data science developed at the Green Bank Telescope the NSF. "