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Around a quarter of a million years after the Big Bang, the very first molecule, helium hydride was formed. Now scientists have confirmed that molecule is still being made, and they found it with some help from a high flying airplane.

Host: Caitlin Hofmeister

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[ ♪ Intro ].

Almost 14 billion years ago, the universe began with a big bang. And while that was great and all, the real space news lately has been about what happened around a quarter of a million years later.

By then, the newborn universe had finally cooled down enough for neutral, uncharged atoms to form. And at some point, those atoms combined. Specifically, helium atoms combined with charged hydrogen ions to make the very first molecule: the helium hydride ion, called HeH+ for short.

Then, this molecule went on to shape the first stars and galaxies, and the rest is history. Of course, this story was originally just based on our understanding of chemistry; no one was actually there to see this happen. And that led to a conundrum.

Because after decades of searching, scientists had found no definitive evidence of helium hydride ions in space at all. That is, until now. In a paper published last week in the journal Nature, an international team has reported that they have finally detected this elusive ion!

Now, to be clear, scientists knew that helium hydride ions could exist, because they were created in the lab way back in 1925. They just hadn't been found anywhere in interstellar space. A big part of the reason is probably that is probably because these ions are incredibly reactive.

Helium hydride is the strongest known acid, and it'll react with any other neutral molecule it encounters. And a single electron will break it apart. In fact, the only thing it won't react with is another positively-charged ion.

So we didn't expect this search to be easy. Still, it's not like scientists were being unreasonable. They weren't looking for the literal first molecules in the universe, since those helium hydride ions are long gone.

Instead, they were studying places with conditions similar to that of the early universe, and were trying to search for these ions there. They even had the perfect place to look: the insides of planetary nebulas. These are beautiful shells of gas cast off by dying stars, and they typically surround a hot white dwarf star.

The white dwarf drives intense waves of radiation into the nebula, which are strong enough to rip electrons from atoms and create huge regions of ionization, where some interesting chemistry can take place. It doesn't create exactly the same conditions as in the early universe, but it's the closest we're likely to get. One especially promising nebula has been NGC 7027, which is about 3000 light-years away.

This nebula is only around 600 years old, which means it's still really dense, and its central star is one of the hottest we know of, burning at nearly 190,000°C. With all that dense gas and extreme radiation, researchers have thought for a while that this nebula would create the ideal conditions for helium hydride to form. But recently, the problem hasn't been so much where to look for these ions as how to actually see them.

Astronomers are normally able to detect molecules in space by tuning in to the characteristic frequencies that they vibrate at. The problem is, helium hydride vibrates the strongest at incredibly high frequencies more than 2 Terahertz. That puts its emissions in the far infrared part of the electromagnetic spectrum.

And while some of our space telescopes have been able to detect far infrared light, they haven't been sensitive enough to distinguish helium hydride ions from similar molecules. To make the situation even more complicated, things like water vapor in the Earth's atmosphere are really good at absorbing infrared radiation, so any instruments here on the ground are more or less useless. But we did detect helium hydride ions.

And to do it, we used a great piece of cutting-edge tech onboard a flying observatory! It's called GREAT, and it's a new, super sensitive receiver able to detect vibrations at more than 2 Terahertz. It was launched onboard SOFIA, a type of Boeing 747 jetliner that NASA modified to carry an almost 3-meter telescope.

Even though SOFIA is still in the atmosphere, it flies more than 12 kilometers above the ground, which is above most of the atmosphere's infrared-absorbing water. Also, the good thing about using a plane instead of a satellite, is that new detectors can easily be installed, without the need for expensive and risky rocket launches. So GREAT was installed on SOFIA and linked to its telescope, and together, they collected data from NGC 7027 for over an hour across three flights in 2016.

Then, the processed data confirmed what astronomers had hoped to find: that clear spectral signature of the elusive helium hydride ion. This detection has helped put everyone's mind at rest about what happened just after the Big Bang, but that's not the only reason it's important. It's also helping astronomers figure out how molecules form and are destroyed in these heavily radiated environments.

And now that we have the tech to spot helium hydride ions in planetary nebulas, we can really study it. We can start to understand the processes from the dawn of chemistry in more detail. Which is good news for scientists past and present and future!

Speaking of great news, if you love learning with us here at SciShow,. I think you'll probably enjoy our podcast. It's called SciShow Tangents.

It's co-produced by me and my buddy Sam Schultz, and created as a collaboration between Complexly and WNYC Studios. It's hosted by Hank and Sam, along with Stefan Chin from the main SciShow channel and Ceri Riley, who's a bonafide genius and writes for SciShow and Crash Course. In every episode, these four show up with the most mind-blowing facts they can find about a topic and try not to go on too many tangents, but even their tangents are really fun and interesting.

They also answer audience questions, make up science poems, and go head-to-head in Truth or Fail. That's a segment where somebody presents two fake science facts and one real one, and the other hosts have to figure out which one is the true fact. Which is surprisingly difficult, because the made-up facts are very convincing.

Listening to SciShow Tangents feels like hanging out with your hilarious and super smart friends. New episodes come out every Tuesday and you can listen wherever and however you like listening to podcasts. [ ♪ Outro ].