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I'm not saying it's aliens....and it's probably not aliens. Also, an update about the most recent SpaceX explosion!

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Video of the explosion:

[SciShow intro plays]

Caitlin: You might have seen some weird space news headlines going around over the last couple of weeks. You know, the ones with words in all caps and lots of exclamation marks? Some of these headlines were saying that astronomers officially announced they’ve finally found evidence of alien life. Which would be super exciting, if that was what they actually announced. But the real story, like always, is a little more complicated.

It all has to do with the light coming from other stars. Stars might look red or blue to our eyes and in pictures, but they actually emit a huge range of wavelengths of light. By breaking a star’s light back up into those different wavelengths, astronomers can see things like how much red light a star puts out, how much blue, and how much of any other wavelengths like ultraviolet light or x-rays.

That’s called a star’s spectrum, and it’s used to measure things like what the star’s made of and how hot it is. But back in 2012, an astronomer named Ermanno Borra predicted that alien civilizations around a star could make themselves stand out by affecting the light that would be detected from their star system. By pointing something like a laser out into space and turning it on and off really fast -- like, a quadrillion times a second fast -- they would make an unmistakable imprint on the spectrum we measure from their home star.

Instead of being a mostly smooth transition across all the different colors, there would be certain specific colors with much more light than the star could produce naturally. It wouldn’t just be at the wavelength of the laser, either. These peaks, as they’re called, would show up throughout the spectrum.

So Borra and another astronomer, Eric Trottier, started searching through the two and a half million spectra in the Sloan Digital Sky Survey for these sorts of telltale signatures. They published their results a few weeks ago in Publications of the Astronomical Society of the Pacific. The vast majority of stars seemed completely normal, which would make sense — even if there were tons of alien civilizations out there, odds are they wouldn’t all be signaling in the exact same way.

But 234 of the stars in the survey showed exactly the type of peaks the astronomers were looking for — exactly the kind we’d expect if there were civilizations orbiting those stars, messing with light. And just about all of the signals came from stars like the Sun, which we know can support intelligent life. So yes, in theory, it’s possible these signals are signs of alien life.

But they aren’t very convincing signs, and there are lots of other possibilities. For one thing, the peaks could have come from the way the team analyzed the spectra, although in that case there would probably be more than just 234 glitches. There could also be something about the stars themselves that we don’t know or understand yet. Or they could have clouds of gas with strange molecules in them, which would also affect their spectra. The research team thinks all of those possibilities are pretty unlikely given what we know about the stars. But other researchers are saying they need much more evidence.

So teams of astronomers are going to be checking out the stars to see if they see the same sorts of signals, and to see if there’s anything else weird going on with them. Meanwhile, here on Earth, we have enough trouble getting people out of low-Earth orbit. One company trying to change that has been SpaceX, and its Falcon 9 rocket exploded during a pre-flight test at the beginning of September.

SpaceX -- with help from NASA, the Federal Aviation Association, and the US Air Force -- has spent the last couple months trying to figure out what happened. It was a complicated accident, and they’ve considered everything from failed parts to foul play. And now, two months later, they’re starting to get some idea of what caused the explosion.

According to a statement released last week, the problem was with a tank storing high-pressure liquid helium on the rocket. The rockets use helium in a bunch of different places, and it’s supposed to be stored using what are called composite overwrapped pressure vessels, or COPVs. The COPVs are supposed to hold the helium inside tanks of liquid oxygen, which is one of the components of the rocket’s fuel.

But helium is a tricky thing to contain -- especially at incredibly high pressures. Helium atoms are so small that they can wriggle through just about any tiny imperfection in whatever they’re being stored in. That’s what SpaceX thinks happened with the Falcon 9. Some liquid helium leaked, causing a rupture in the COPV that led to the explosion.

SpaceX’s engineers have been able to reproduce the problem back in a lab, but they’re still searching for what exactly went wrong with the launch-- and how to fix it. But they’re aiming to be ready to launch another rocket before the end of the year. So here’s hoping they figure this out soon.

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