Negative Discovery Proves Positive in Cosmic Search
An artist illustration of the cosmic chemistry cycle. Stars eject matter into space, which forms giant gas and dust clouds. The clouds condense into planets and stars, comets and meteorites.
Credit: Bill Saxton, NRAO/AUI/NSF

The discovery of a long-sought molecule with a negative charge, the first-ever pinpointed in the depths of interstellar space, may just be the tip of an iceberg for researchers studying the chemistry of the cosmos.

"It's kind of intoxicating because it's not just a solitary discovery," astronomer Patrick Thaddeus, of the Harvard-Smithsonian Center for Astrophysics (CfA), told "It's opening up a whole avenue of study."

Known as an anion, the negatively charged molecule joins a host of other molecules--130 neutral and 14 positively charged--known to exist in interstellar space. Astronomers believe a simple hydrogen anion is continuously formed and destroyed in our nearby Sun, but had not found negatively-charged molecules elsewhere in the universe, Thaddeus added.

"We've spotted a rare and exotic species, like the white tiger of space," said CfA astronomer Michael McCarthy, who led the study, said in a statement.

Tracking down molecules in space may sound as exciting as counting sand grains on a beach. But the search can yield a wealth of information on how the chemical ingredients so vital for life arise in the universe.

Earlier this year, researchers found that a series of organic molecules important for life formed in the gas and dust clouds that later lead to stars and planets.

McCarthy, Thaddeus and their colleagues used the Green Bank Telescope to hunt down a large molecule--relatively speaking--known as C6H- in the gas shell of a red giant star sitting in the constellation Leo, as well as in a cold molecular cloud in the Taurus constellation.

In order to pinpoint C6H-, which is a long chain of six carbon atoms attached to a hydrogen atom sporting an extraneous electron, McCarthy and his team identified its radio signature on Earth, and then used it as a template for comparison to space-based sources.

Thaddeus said the research team has templates for three other negatively charged molecules and is itching to search for their space-based versions.

"It opens up the whole question of negative ions in interstellar space," Thaddeus added.

The research was detailed in the Dec. 1 issue of The Astrophysical Journal Letters.

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