About 10 to 25 percent of the carbon in space is believed to be found in PAHs, which contain at least two carbon rings, but the infrared signals weren’t distinct enough to identify specific molecules. Starting in the 1980s, astronomers have used telescopes to detect infrared signals that suggested the presence of aromatic molecules, which are molecules that typically include one or more carbon rings. The research team also includes scientists from several other institutions, including the University of Virginia, the National Radio Astronomy Observatory, and NASA’s Goddard Space Flight Center. Michael McCarthy, associate director of the Harvard-Smithsonian Center for Astrophysics, is another senior author of the study, which appears today in Science. “What makes the detection so important is that not only have we confirmed a hypothesis that has been 30 years in the making, but now we can look at all of the other molecules in this one source and ask how they are reacting to form the PAHs we’re seeing, how the PAHs we’re seeing may react with other things to possibly form larger molecules, and what implications that may have for our understanding of the role of very large carbon molecules in forming planets and stars,” says McGuire, who is a senior author of the new study. This discovery suggests that these molecules can form at much lower temperatures than expected, and it may lead scientists to rethink their assumptions about the role of PAH chemistry in the formation of stars and planets, the researchers say. But the interstellar cloud where the research team observed them has not yet started forming stars, and the temperature is about 10 degrees above absolute zero. PAHs were believed to form efficiently only at high temperatures - on Earth, they occur as byproducts of burning fossil fuels, and they’re also found in char marks on grilled food. Now, a team of researchers led by MIT Assistant Professor Brett McGuire has identified two distinctive PAHs in a patch of space called the Taurus Molecular Cloud (TMC-1). Since the 1980s, circumstantial evidence has indicated that these molecules are abundant in space, but they have not been directly observed. Much of the carbon in space is believed to exist in the form of large molecules called polycyclic aromatic hydrocarbons (PAHs).
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