A Cosmic Recipe for Life’s Origins

How do solar systems begin? How does life begin? Worcester State Professor Andrew Burkhardt tuned into radio signals from space to bring us enticingly closer to the answers.

Assistant Professor of Astronomy Andrew Burkhardt. Photo by George Annan ’21.

By Nancy Sheehan 

In the vast expanse of the universe, where stars are born and planets take shape, a class of molecules known as polycyclic aromatic hydrocarbons is playing a crucial role in unraveling the mysteries of cosmic chemistry and the origins of life on Earth.

Andrew Burkhardt, assistant professor of astronomy at Worcester State, along with researchers from MIT and other universities, have made a major discovery of complex aromatic molecules, including the stable four-ring molecule cyanopyrene, in the Taurus molecular cloud, located 430 light years from Earth.

The groundbreaking discovery represents a significant leap forward in understanding the size and complexity of organic molecules detected in the cold, dark regions of space where new stars form. The research team’s findings were recently published in Science, one of the world’s most prestigious science journals, and Nature Astronomy, which publishes top-tier research in the field.

Carbon is a fundamental building block for creating the molecules that make up living things, like plants and animals. Detecting large, carbon-rich molecules such as cyanopyrene in space helps scientists understand how the building blocks of life form, Burkhardt said.

The scientists studied the Taurus molecular cloud because it is similar to the types of clouds from which solar systems form, as ours did billions of years ago. As Burkhardt explains, finding polycyclic aromatic hydrocarbons (PAHs) in space provides evidence for the presence of the “best primordial soup” for the origins of life. The greater the complexity of molecules detected, the more optimistic scientists can be about the chances of life forming from these building blocks.

The discovery of cyanopyrene in this cold, dark Taurus cloud of gas and dust provides clues about how the chemical building blocks for planets and life may have formed in our own solar system, he said. 

“This discovery gives us insights into the early stages of solar system and planet formation and how the materials that make up planets like Earth may have originated from ancient interstellar clouds,” Burkhardt said. “Ultimately, finding these large carbon molecules in space brings us closer to unraveling the mysteries of how planets and even life can form in the universe.”

The cyanopyrene molecule is a type of PAH. In this context, it offers insights into the distribution of carbon throughout the universe, Burkhardt said. Specifically, the discovery suggests that much of the carbon in our solar system may have originated from ancient interstellar clouds, providing crucial clues about the chemical building blocks of planets and life.

“What we’ve found is that these PAHs, which are essentially large aromatic molecules, are not just present in space but are becoming increasingly complex,” Burkhardt said. Before he and his colleagues identified the four-ring molecule, no scientist had ever detected such a large PAH in space.

An artist’s impression of the four-ring molecule cyanopyrene. Illustration courtesy of NSF/NSF NRAO/AUI/S.Dagnello.

Aromatic Clues in Space

The discovery of this four-ring cyanopyrene molecule is a significant milestone in astrochemistry. To start, it pushes the boundaries of what we thought was possible in the harsh conditions of space. Perhaps even more importantly, it provides crucial insights into the formation and evolution of these complex organic compounds.

PAHs such as cyanopyrene are important because they appear to be ubiquitous in the universe and may have played a role in the origins of life, and their specific molecular properties and abundances offer valuable clues about the chemistry of our early solar system and the evolution of complex organic molecules in space.

“The fact that we’re finding these larger and more intricate PAHs is really exciting,” Burkhardt said. “It suggests that the chemistry in these cold, dark molecular clouds is much more robust than we previously believed. And it raises the tantalizing possibility that the building blocks for life may be more abundant than we ever imagined.”

It would be difficult to overstate the importance of PAHs in the cosmic story, he said. These molecules are believed to be the precursors to even more complex organic compounds, such as amino acids and nucleic acids—the fundamental building blocks of life as we know it.

“When we look at the composition of comets and asteroids, we see clear evidence of these aromatic molecules,” Burkhardt explained. “And when we analyze the chemistry of these objects, we find the same kinds of organic compounds that are essential for life on Earth. It’s as if the universe is providing us with a cosmic recipe for the origins of life.”

In chemistry, aromatic describes a molecule that contains one or more ring-like arrangements of carbon atoms with a specific electronic structure that confers stability. The term aromatic comes from the fact that many of the first discovered of these compounds had distinctive smells. However, the term now refers to structural characteristics, not scents.

The discovery of the four-ring molecule is just one of the groundbreaking findings that have emerged from the research team. In 2018, they reported the detection of the first-ever aromatic molecule found in the interstellar medium using radio astronomy, a milestone that paved the way for the current study.

“What’s really exciting is that we’re not just finding these molecules, but we’re also starting to understand how they form and evolve,” Burkhardt said. “By studying the relative abundances of different PAHs, we can piece together a picture of the chemical processes that are taking place in these extremely cold clouds—processes that may have played a crucial role in the formation of our own solar system and the emergence of life on Earth.”

Burkhardt said that, as scientists better understand how aromatic molecules form and evolve, they gain insights into the early stages of planet formation. Knowing where the “Lego pieces” that build planets come from can help scientists understand the right environments for planets like Earth to form, he said.

The Largest Steerable Telescope

For the study, the researchers used the Green Bank Telescope in West Virginia, which can detect faint radio signals given off by molecules in space. The telescope, which measures 110 meters across, is the largest steerable object employed on land.

“The only things bigger that humans can steer are aircraft carriers and oil tankers,” Burkhardt said. The massive dish on the Green Bank Telescope acts as a giant antenna, collecting even very weak signals from molecules in other parts of our galaxy—and even in other galaxies. The larger the telescope, the fainter the signals it can detect.

Because their previous findings were so significant, the team was able to get over 1,000 hours of observation time on the telescope, which is much more than the typical 10- to 50-hour slots, allowing them to examine their target source in greater depth.

For Burkhardt and his colleagues, the journey of discovery is far from over. In fact, this April they announced the first-ever detection of the seven-ring molecule cyanocoronene in space. The potential implications of their work are both humbling and inspiring. 

“These complex organic molecules that we’re finding in space are the same kinds of molecules that are essential for life on Earth,” Burkhardt reflected. “It’s a reminder that we’re all connected, that we’re all made of stardust, and that the chemistry of the universe is inextricably linked to the chemistry of life. And that’s a truly remarkable thing to ponder.”