Surprising Chemicals Found among Stars
 

Astronomers are making some surprising chemical finds among stars—discoveries that they say add to the number of known ways in which molecules needed for life could form.

In less than a year, researchers say they have found the first three molecules in space with negative electrical charge. Such molecules have an excess of electrons, negatively-charged subatomic particles.

“This discovery continues to add to the diversity and complexity that is already seen in the chemistry of interstellar space,” said Anthony J. Remijan of the Charlottesville, Va.-based National Radio Astronomy Observatory.

“It also adds to the number of paths available for making the complex organic molecules,” the ingredients of life, he added. Such substances are thought to have formed in the same giant clouds that give rise to stars and planets.

In the July 20 issue of the research journal Astrophysical Journal Letters, two teams of astronomers announced finding the third negatively charged chemical, known as octatetraynyl anions.


Artist's diagram showing models of negatively charged molecules near a star. The long, straight model underneath the downward-pointing arrow represents the newfound octatetraynyl anion. See here for a full diagram showing how it forms.

The molecules are recognizable by characteristic frequencies, or energies, of radio waves that they emit, scientists said.

The molecules, which consist of chains of eight carbon atoms and one hydrogen atom, turned up in the envelope of gas around an old star and in a cold, dark cloud of molecular gas. The researchers used data from the National Science Foundation’s Robert C. Byrd Green Bank Telescope in Green Bank, W. Va.

Previously, only molecules with neutral or positive charge were known. A neutral molecule has just enough electrons to cancel out positive charges within the atoms of the molecule. Positive molecules have fewer than this number of electrons; negative molecules, more.

About 130 neutral and about a dozen positively-charged molecules have been discovered in space, but the first negatively-charged molecule was not discovered until late last year, researchers said. Among the negatively charged molecules, the newfound one is the largest.

“Until recently, many theoretical models of how chemical reactions evolve in interstellar space have largely neglected the presence of anions,” or negatively charged molecules, said Jan M. Hollis of NASA’s Goddard Space Flight Center in Greenbelt, Md. “This can no longer be the case.” It was previously thought that ultraviolet light would knock extra electrons off any molecules, preventing any from taking on a negative charge.

Hollis and Remijan are members of one of the research teams reporting the findings in Astrophysical Journal Letters. The other team consisted of researchers with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.