Right after the Big Bang, only a small number of types of atoms existed, including helium and hydrogen. A major milestone in the development of the early universe was the time, around 100,000 years after the Big Bang, that these two atoms combined. The helium and hydrogen atoms combined to form a molecule called helium hydride.
It would be expected that helium hydride would still be present in some parts of the universe. But strangely enough, it has never been detected in space before now.
Now the molecule has finally been detected by SOFIA, the Stratospheric Observatory for Infrared Astronomy. SOFIA is an observatory aboard an airplane, which allows it to fly above much of the water vapor in Earth’s atmosphere. This means it can peer farther out into the depths of space.
To locate the helium hydride, SOFIA searched the remnants of a star that was once like our Sun. The planetary nebula NGC 7027 is 3,000 light-years away, in the Cygnus constellation, and its conditions allowed the formation of the detected helium hydride.
“This molecule was lurking out there, but we needed the right instruments making observations in the right position — and SOFIA was able to do that perfectly,” Harold Yorke, director of the SOFIA Science Center in California, said in a statement.
This finding has relevance to our understanding of the chemistry of the early universe and how it evolved over the years.
“The lack of evidence of the very existence of helium hydride in interstellar space was a dilemma for astronomy for decades,” Rolf Guesten, lead author of the paper from the Max Planck Institute for Radio Astronomy, in Bonn, Germany, said in the same statement.
“It was so exciting to be there, seeing helium hydride for the first time in the data,” Guesten said. “This brings a long search to a happy ending and eliminates doubts about our understanding of the underlying chemistry of the early universe.”
The findings are published in the journal Nature.