Scientists finally found the first ever molecule of the universe using a telescope that we fly around the world on a plane and that’s a real sentence. Just let that sink in a little bit. That’s the world we live in these days. The molecule in question is called helium hydride (HeH+) and the fact that we have finally detected it in space confirms some of our theories about the behavior of the early universe. It could help us understand more about how the first stars and galaxies formed.
If we start at the literal beginning, the universe was a small singularity, a point of infinite temperature and density. Maybe one second after the Big Bang. Which was something akin to an explosion but we can’t exactly describe it as that. We have got a flaming hot soup of particles. About 5 and half BILLION degrees Celsius, to be precise. A couple minutes in, the universe is mostly helium but everything is ionized because there are too many high-energy photons. They are flying around immediately knocking off any electrons that may want to bind to the nuclei of different elements to make them neutral. But things have calmed down since then.
How the first ever molecule of the universe formed?
In the almost 14 billion years since the Big Bang, the universe has cooled and expanded. As far as we know, will continue to do so. About 380,000 years in, give or take a few, everything cooled and slowed down enough that electrons were able to stably bind to a helium nucleus. And we have the first stable atom. So, we have stable helium and a bunch of unstable H+, the ionized form of hydrogen that hasn’t gained its electron yet. And it’s looking for a friend to share an electron. It’s helium with two electrons, and hydrogen thinks it just might want one! So, the two get together to form the universe’s very first molecule: Helium Hydride (HeH+).
This is where the chemistry stops being fun to think about on just the atomic level. It has galactic universal consequences. As things continue to cool down, neutral hydrogen atoms become common because their electron can finally stay attached. Energetically speaking, it’s now more efficient for hydrogen to form molecules with itself, forming H2, than it is to glom on to helium to form helium hydride. That means helium hydride starts to disappear, giving way to high amounts of molecular hydrogen. Which is, arguably, the beginning of our modern universe. Being a fundamental component of things like H2O, vital for beings like us, of course.
For astronomers, helium hydride is an essential in-between step from the beginning to the now. It’s also thought that the formation and then breakdown of this molecule, could have been one of the main mechanisms through which all the hot gases of the universe could cool down enough to form stars in the first place. And while scientists first started studying the creation of helium hydride in the lab back in 1925, astronomers have not been able to find traces of it in space until now. This latest news is the first-time helium hydride has been detected in its natural environment.
How it was detected?
Researchers used the Stratospheric Observatory for Infrared Astronomy, or SOFIA—which is basically a high-altitude plane carrying a bunch of exciting equipment that helps us look at space. SOFIA carries one particular instrument called the German Receiver for Astronomy at Terahertz frequencies (GREAT), which researchers pointed at white-hot dying stars. And there it is, helium hydride hanging out in planetary nebula NGC 7027.
HeH+ emits its strongest spectral line at a frequency of 2.01 THz, which Earth’s atmosphere can block. To get past that, scientists have now used NASA’s SOFIA, which can scour the cosmos from its perch onboard a Boeing 747SP. Since this mobile observatory flies at an altitude of up to 45,000 ft (13,700 m), it can get an unobscured view of the required infrared wavelengths.
It’s important to point out that the helium hydride being proclaimed in the headlines is not actually the exact same molecule from the beginning of our universe. I mean, yes, they are both helium hydride, but it’s not the same helium hydride molecule. All of that first helium hydride molecules made at the beginning of the universe have long since been broken apart and these are ones that exist because these star environments are hot enough to ionize hydrogen and make it possible for helium hydride to exist again.
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GREAT was able to see what we have been trying to get a glimpse of for decades because SOFIA operates at high enough altitude that Earth’s atmosphere doesn’t get in the way of the kinds of signals it’s trying to detect, but it also is able to come down to Earth and get upgrades. Unlike space telescopes which we have sent out into the dark with no way to recover them and install new technology. A new development in terahertz technology is what allowed us to perform this kind of spectroscopy at the required wavelength.
It’s thanks to brand new tech like this that we are able to confirm our current ideas about the universe’s first moments and has led to a discovery of the first ever molecule of the universe. Hopefully this will give us an even better understanding of the formation of early stars and galaxies.