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Oxygen in space

August 4, 2011

Scientists have detected oxygen molecules in the star-forming region of Orion. Researchers believe frozen dust particles consisting of oxygen atoms evaporated in the heat of budding stars to form molecules.

Herschel spacecraft
ESA's Herschel spacecraft has discovered molecular oxygenImage: picture-alliance/dpa

In a new scientific paper published on Monday, the European Space Agency's (ESA) Herschel spacecraft has discovered oxygen molecules in space. The findings were published in the August 1 edition of Astrophysical Journal.

While oxygen in its atomic form exists in water and carbon monoxide - and according to researchers is therefore the third most abundant element in the universe - ESA's Herschel mission has discovered the first molecular instance of oxygen space. That is, two oxygen atoms bound together to form the dioxygen (O2) molecule.

The oxygen molecules were discovered in the Orion star-forming region. However, they are few in number. The scientists used three infrared frequencies emitted by Herschel's far-infrared instrument and found one oxygen molecule for every million hydrogen molecules within gas and dust surrounding Orion's forming stars.

The scientists had decided to search Orion based on the theory that heat from the constellation's forming stars would evaporate ice from tiny dust grains to form oxygen molecules.

The largest single mirror ever built for a space telescope is aboard the Herschel spacecraft, which collects "long-wavelength radiation from some of the coldest and most distant objects in the universe," according to the ESA.

Rho Ophiuchi star formation
Bérengère Parise and her research team recently found hydrogen peroxide in the Rho Ophiuchi star formationImage: ESO/S. Guisard

'Hiding' oxygen

According to Göran Pilbratt, a Netherlands-based ESA scientist on the Herschel project, the scientists hope to find out where else in space oxygen molecules may have formed.

"It will certainly be of considerable interest to establish abundances of O2 in different environments to be able to understand what is going on," he told Deutsche Welle in an e-mail. "Obviously non-stationary processes must be at play. We already now know for a fact a lot of the oxygen must exist in other forms than O2."

Pilbratt added that scientists long suspected oxygen molecules exist in space, but have been baffled by their inability to find them. NASA's Submillimeter Wave Astronomy Satellite and Sweden's Odin mission have both searched so far, without any results.

"Stationary chemical models indicate that a lot of the oxygen in the interstellar medium ought to exist in the form of O2, but previous searches showed this not to be the case, providing upper limits two orders of magnitude lower than the expected abundances," he said.

Other space scientists have been encouraged by this result. Bérengère Parise, a French researcher based at the Max Planck Institute in Bonn, whose team last month revealed the presence of hydrogen peroxide in space, said that this new finding is a positive step.

"This discovery will allow astrochemists to refine their models and better understand the chemical interplays between gas and dust particles in interstellar clouds, as well as to understand how much material is frozen out onto the surface of cold dust particles," she wrote in an e-mail sent to Deutsche Welle.

"A measured abundance is always much more constraining for models than an upper limit based on non-detections (as was available in the past)," she added. "Star formation theories will also have to take into account the observed abundance of oxygen in the computation of the cooling rates."

NASA's California-based Paul Goldsmith, one of leaders of the international team of investigators, said finding the oxygen molecules opens the door to further questions.

"We didn't find large amounts of (oxygen molecules), and still don't understand what is so special about the spots where we find it," he said in a statement. "The Universe still holds many secrets."

Author: Gerhard Schneibel
Editor: Cyrus Farivar