Study Finds Way To Observe Ion Responsible For Early Star Formation
April 14, 2012

Study Finds Way To Observe Ion Responsible For Early Star Formation

Researchers from the University of Arizona (UA) claim that they have found a way to observe the triatomic hydrogen ion believed to be the key element responsible for the formation of the first stars following the Big Bang.

According to an article published to the UA News website on Wednesday, the molecule, which is known as H3+, is an ion that consists of three hydrogen atoms with just a pair of electrons to share between them, giving it a positive charge. It is believed to be the catalyst for many chemical reactions, including those which ultimately result in compounds such as water or carbon, according to the university researchers.

"Most of the universe consists of hydrogen in various forms, but the H3+ ion is the most prevalent molecular ion in interstellar space. It's also one of the most important molecules in existence," Ludwik Adamowicz, a professor in the UA Department of Chemistry and Biochemistry who supervised the research, said in a statement.

The university researchers, who recently published their findings in the journal Physical Review Letters, say they did not set out looking for this supposed cosmic building-block.

"It all happened almost by chance," said Michele Pavanello, a doctoral candidate at UA at the time and now assistant professor of theoretical chemistry at Rutgers University. "A friend of the mass-spectrometry facility in the UA's chemistry department happens to be a very good quantum chemist from Hungary. He once visited the department and talked to Ludwik about the possibility to do some H3+ calculations."

"At the time, I had just started. The code I was writing was almost done, and we thought H3+ could be a good system on which to test this code," he added.

As part of their work, Pavanello and his colleagues input code into supercomputers at a computer center at the Arizona university, describing how H3+ vibrates according to the principles of quantum mechanics.

Pavanello said that by altering the level of approximations made in said computer code, they can develop programs which can precisely describe the motion of small molecules -- as they did in this study -- or approximate the movements of much larger ones.

"The UA team's contribution allowed the researchers for the first time to assign spectral lines of H3+ to particular types of the vibrational motions as the ion releases photons with near-visible wavelengths. These wavelengths contribute to the color of the light H3+ radiates toward us from interstellar space," the UA press release said.

"Knowing the vibrational levels, and therefore the spectral lines of H3+, will allow astronomers and astro-chemists to sift through the inundation of spectral lines and further identify the elemental composition of objects in space," the university added. "It also allows scientists to predict the cooling abilities of H3+, and generate a possible scenario for how the first generation stars formed after the Big Bang."

The research is vital because scientists believe that without H3+, early stars would have never formed. They would simply have gotten hotter and hotter until they exploded, Pavanello said. However, they believe that the triangular-shaped, triatomic hydrogen ion, which would have been one of a handful of molecules that existed at the time, was responsible for cooling down the potential star by emitting light.

"We now have an important piece of the puzzle needed to embark on reliable modeling of the formation of the first stars," Pavanello said.


Image Caption: The molecule known as H3+ is believed to have had a vital role in cooling down the first stars of the universe, and may still play an important part in the formation of current stars. Above, new stars burst into being in the star-forming nebula Messier 78, imaged by NASA's Spitzer Space Telescope. (Image credit: NASA/JPL-Caltech)