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Fluoride Molecules Detected In Space

August 12, 1997
Johns Hopkins University
Astronomers, using a satellite operated by the European Space Agency, have made the first detections of fluorine in space. The element is contained in hydrogen fluorine molecules in a giant gas cloud near the center of out Milky Way galaxy.

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August 7, 1997
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Not only is our water supply fluoridated, but so too,apparently, is our galaxy.

A team of astronomers from the United States and Germany,led by Johns Hopkins astrophysicist David Neufeld, has discoveredtrace amounts of hydrogen fluoride gas in the near vacuum ofinterstellar space, using a satellite built and launched bythe European Space Agency and operated by ESA with NASA's participation.Although approximately 100 different kinds of molecules have been detectedin interstellar space over the past 30 years, the discovery ofhydrogen fluoride marks the first time that a molecule containingfluorine has been detected in an interstellar gas cloud. It is also thefirst time that a new interstellar molecule has been detected byobservations at far-infrared wavelengths.

The discovery will be reported in an article that is toappear in October in the Astrophysical Journal Letters.

The astronomers searched for hydrogen fluoride moleculeswithin a giant cloud of interstellar gas located near the centerof the Milky Way galaxy, using ESA's Infrared Space Observatory satellite,which was launched in November 1995. The new observations were carried out inMarch 1997 with the Long Wavelength Spectrometer, one of four instruments onboard ISO. Looking in the far-infrared region of the electromagnetic spectrum,the astronomers observed the telltale signature of absorption by trace amountsof hydrogen fluoride gas.

"Because the Earth's atmosphere is completely opaque tofar-infrared radiation, the observations that we carried out arepossible only from space," said Neufeld, a professor in the Johns?ŠHopkins Department of Physics and Astronomy. "The ISO satellitehas opened up an exciting new window on the universe by allowingus to observe at far-infrared wavelengths."

In concentrated liquid form, hydrogen fluoride -- orhydrofluoric acid as it is known when dissolved in water -- isfamiliar to laboratory chemists as an extremely dangerous andcorrosive acid that dissolves glass and severely burns humantissue. The ISO's sensitive spectrometers enabled the astronomersto detect hydrogen fluoride in interstellar space even though itsconcentration was less than one part per billion.

The characteristic wavelength at which hydrogen fluoridemolecules absorb radiation is about one two-hundredth of an inch,much larger than the wavelength of visible light but far smallerthan the wavelengths typically used for radio and televisioncommunications.

The gas cloud in which hydrogen fluoride molecules werediscovered lies about 20,000 light years from Earth, in thesouthern constellation Sagittarius. Known to astronomers asSagittarius B2, the gas cloud is composed primarily of hydrogenmolecules. As in other clouds of interstellar gas, theenvironment in Sagittarius B2 is extreme by earthly standards, with temperatures less than minus 370 degrees Fahrenheit, andpressures more than one hundred trillion times smaller than theatmospheric pressure on Earth.

"This discovery gives us the opportunity to study thechemistry of fluoride molecules in the frigid conditions thatcharacterize the near vacuum of interstellar space," Neufeldsaid. "One of the key questions is how these molecules wereformed. Our analysis suggests that the hydrogen fluoride wedetected was produced by direct chemical reactions betweenfluorine atoms and hydrogen molecules. Unlike most atoms,fluorine atoms are extremely reactive and attack the relativelyinert hydrogen molecules that are the principal constituent ofthe interstellar gas. The result is hydrogen fluoride."

The other members of the team that made the hydrogenfluoride discovery are professors Jonas Zmuidzinas and ThomasPhillips of the California Institute of Technology, and Dr. PeterSchilke of the Max-Planck Institute for Radio Astronomy in Bonn,Germany. The participation of Neufeld, Zmuidzinas and Phillips asguest observers on the European satellite was supported by theNational Aeronautics and Space Administration.

Further information is available from Professor Neufeld at(410) 516-8582, or by e-mail at His Web address is

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