Astronomers from UMass Amherst Find Rare, Interstellar Molecule

AMHERST, Mass. - Astronomers at the University of Massachusetts have discovered a rare molecule in interstellar space, within the dense, gaseous clouds where new stars form. Professor William Irvine, graduate students James Dickens and Albert Nummelin, and colleagues in Sweden and Japan, reported finding ethylene oxide in three different interstellar clouds thousands of light-years away, in the Milky Way galaxy. The molecule is unusual in terms of both its structure and its chemistry.

Many types of molecules have been found in interstellar space, but this particular molecule is unusual, according to the UMass scientists, because it’s formed like a ring – scientists call it a "cyclic" molecule. Only four of the 100 interstellar molecules that have been identified are cyclic. "Scientists are asking, ‘Why aren’t there more?’ It’s puzzling," said Dickens. Perhaps cyclic molecules exist abundantly in space, but current technology cannot detect them, he added. Furthermore, this molecule is different from the other cyclic molecules seen in space. Those cyclic molecules are comprised of carbon, hydrogen, and silicon; the ethylene oxide molecule also includes oxygen. This makes the newly discovered molecule the most complex cyclic molecule found in space so far, said Irvine.

Although ethylene oxide is rare in space, it is not unfamiliar on earth, according to Irvine. The chemical, which is a gas at room temperature, is toxic to microorganisms, but not to larger organisms, such as human beings, he said. It is used in industry to sterilize objects that cannot be heated. The Viking spacecraft is one example: heat would have damaged the spacecraft’s electronics, Irvine said.

The discovery raises some interesting issues, according to Irvine. "For instance, stars produce atoms but not molecules, so how are these molecules produced?" Perhaps even more intriguingly, ethylene oxide is related to a forerunner of sugarphosphates, which make up the backbone of DNA, the genetic coding in all animals, including human beings. "This raises the question about how life began, which has become a respectable scientific question," Irvine said. "It is reasonable to ask whether everything needed to start life was here on earth, or whether something crucial was brought to earth by a meteor or a comet, perhaps containing interstellar material."

The team saw the first evidence of an interstellar ethylene oxide molecule in 1995, then obtained additional data to confirm the finding. The initial finding was described in a recent issue of The Astrophysical Journal. The project relied on cooperation from an international group of astronomers, including those at Onsala Space Observatory in Sweden and the Nobeyama Radio Observatory in Japan. Locally, observations were made from the Haystack Observatory in Westford.