The first molecule in the universe to be created after the Big Bang was discovered for the first time in space. Helium hydride (HeH), a combination of helium and hydrogen, was discovered about 3,000 light-years from Earth with an instrument aboard the Astronomical Observatory for Infrared Astronomy (SOFIA), a telescope built into a converted 747 aircraft Opaque aircraft flies parts of the Earth's atmosphere.
It has long been thought that HeH marks the beginning of chemistry when the remains of the Big Bang cool down to about 4000 K and ions combine with electrons to form neutral atoms. The researchers believe that in this original gas neutral helium has reacted with hydrogen ions to the first chemical bond of the first molecule.
In 1925, chemists synthesized HeH in the laboratory. In the 1970s, theorists predicted that the molecule could exist today, most likely re-formed in planetary nebulae, clouds of gas ejected from dying sun-like stars. But decades of observations found none and raised doubts about the theory.
To find the elusive molecule, astrochemists seek characteristic light frequencies, especially a far-infrared spectral line that is typically blocked by the earth's atmosphere. However, a far-infrared spectrometer aboard SOFIA enabled them to find this signature for the first time in a planetary nebula called NGC 7027 (pictured above), researchers report today in Nature . The result shows that this unlikely molecule – typically with unreactive helium – can arise in space. Once this cornerstone has been confirmed, the next 13 billion years of chemistry seem to be on solid ground.