More than 13 billion years ago, the observable universe exploded into existence in an event known as the Big Bang.
Astronomers have been scrapping together a picture of the young universe after its fiery beginning. For decades, they've been hunting for an important piece of the picture: the very first molecule that ever formed.
The Story Of The Early Universe
Fresh off the Big Bang, only a handful of atoms existed, including hydrogen and helium. Scientists have figured that the two atoms combined to produce the universe's first molecule, helium hydride or HeH+.
However, no one has been able to find traces of helium hydride anywhere in the universe — until now.
"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 from the Max Planck Institute for Radio Astronomy, says in a report from NASA.
Nearly a century ago, scientists created the molecule in the laboratory. Now, they've finally gotten the real thing.
Finding The Priomordial Molecule In The Stars
At long last, astronomers have detected the infrared signature of helium hydride in the heart of a dying star in Earth's very own galactic neighborhood, according to a study published in the journal Nature.
Planetary nebula NGC 7027 lies around 3,000 light-years away from Earth. Planetary nebulae are stars at the final stage of their lives, having burnt out the last of their nuclear energy and slowly shrinking into cool white dwarfs.
For decades, scientists have recognized that NGC 7027 provides the ideal environment for the formation of helium hydride due to its heat and ultraviolet radiation. It took a while for technology to advance enough to confirm these suspicions, though.
To pick up the infrared signature of helium hydride from a planetary nebula thousands of light-years away, scientists made use of ultra-sensitive instruments on NASA's airborne Stratospheric Observatory for Infrared Astronomy or SOFIA. The aircraft flies 45,000 feet in the air, overcoming the barriers of Earth's atmosphere that may block off the specific wavelengths.
Aboard SOFIA is the German Receiver for Astronomy at Terahertz Frequencies or GREAT, which is essentially a radio receiver that was recently upgraded to include the specific channel for helium hydride other telescopes didn't have.
All the astronomers' efforts and technological advancements paid off. Finally, hydrogen hydride's infrared signal is detected clearly across the cosmos.
With the formation of helium hydride, the universe begins to settle and cool down. Eventually, hydrogen atoms combine with helium hydride to create molecular hydrogen, which is known as the building blocks of the very first stars in the universe. The rich, infinite world of the modern universe expanded on from here.
"It was so exciting to be there, seeing helium hydride for the first time in the data," Guesten says. "This brings a long search to a happy ending and eliminates doubts about our understanding of the underlying chemistry of the early universe."