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Remember when astrophysicists thought they'd found signs of life on Venus? A different team re-crunched the numbers, and their results raised some questions about that claim. Also, a bunch of exoplanets are doing a really precise dance around a not-so-distant star!

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Last fall, a team of astronomers made what seemed like a huge announcement: Using powerful radio telescopes, they claimed to have found evidence of phosphine gas in Venus’s atmosphere. On Earth, phosphine is mainly produced by life.

And it’s so fragile that light from the Sun can cause it to break apart. So, phosphine isn’t just an indicator of life on a planet, but a sign that there are living things there now making it! That said, that’s a pretty extraordinary claim.

And scientists have spent a lot of time trying to come up with alternative explanations for how that phosphine got there. But… what if there really isn’t any phosphine at all? That’s what one team is suggesting in a paper accepted to The Astrophysical Journal.

Letters last month. According to their analysis, all this excitement might just be a case of mistaken identity. See, the original research team didn’t send a spacecraft to Venus to sample its atmosphere.

They relied on spectroscopy, which is the study of how matter emits and absorbs light. It’s the standard way astronomers learn about places they can’t easily visit, but it comes with challenges. Spectroscopy works because every atom and molecule emits and absorbs its own unique pattern of light.

But just because those patterns are unique doesn’t mean they can’t be similar. Like, in the case of Venus, the original researchers were observing a radio wave emission with a frequency of 266.94 gigahertz, coming from Venus’s cloud layer. Phosphine absorbs light right around that frequency, but so does sulfur dioxide, one of the most common molecules in the planet’s atmosphere — and one that almost definitely isn’t made by life.

To tell them apart, the researchers had measured another radio frequency, one that’s absorbed by sulfur dioxide, but not phosphine. And they didn’t detect very much absorption. From that, they concluded that there wasn’t that much sulfur dioxide in the region they were studying.

So, voila, it was probably phosphine! To be clear, that’s all good science! But this new paper offers another take on the data.

In it, this team used a computer model to simulate how these signals would appear to the radio telescopes used by the original researchers, based on how the telescopes were configured at the time. And in the end, they suggested that the telescopes’ configurations might have set the first researchers on the wrong track. For one, the authors suggest that the telescopes were configured in a way that weakened the signal from sulfur dioxide, making it seem like there was less of it in the atmosphere than there was.

This is a phenomenon called spectral line dilution, and it happens when a telescope puts less emphasis on common gases spread over a large area. One of the authors just called it a quote, “undesirable side effect” of how the telescope was set up. So, there was probably more sulfur dioxide out there than the first authors thought.

But also, after re-analyzing the shape of the data, this new team noticed that the supposed phosphine signal looked like it was coming from a region of the atmosphere with pretty low pressure — something a lot lower than what you’d find in Venus’s cloud layer. So, they proposed that the signal was actually coming from much higher in Venus’s atmosphere than the scientists thought. Instead of coming from the cloud layer, it was probably coming from the mesosphere.

At that height, sunlight would destroy phosphine molecules within seconds, making phosphine really unlikely to be the source of the signals. This is all nitty-gritty stuff, but details matter and astronomers now have two competing interpretations of the same observations. So, is there phosphine in Venus’ atmosphere?

It’s going to take more observations to find out. Meanwhile, looking much farther away, scientists have also been trying to learn more about the planets around a star called TOI-178. The planets are around 200 light-years away, and there are six of them.

And in a paper published last week in Astronomy & Astrophysics, astronomers announced that five of them are also pretty in-sync. When scientists timed the motion of these planets, they found that several of them had orbital periods that were multiples of each other. Like, for every 18 orbits made by one of the innermost planets, the next one out went around its star almost exactly nine times.

And for every nine times that one went around, the next one out orbited six times. This is called a mean-motion resonance, and we have some of them in our solar system, too. For example, three of Jupiter’s four largest moons follow a similar pattern.

But the resonance at TOI-178 is a lot more complicated. If you look at all five planets, the full resonance is 18 to 9 to 6 to 4 to 3. It’s so well-organized that researchers were able to follow this pattern to find the sixth, outermost planet in this system.

As for how the planets got like this, the researchers think this system has probably had a peaceful existence so far, without any big events to mess up these synchronized orbits. But either way, this pattern isn’t just interesting. Having multiple planets in resonance also makes it easier for astronomers to calculate their mass, using a method called transit timing variation.

Each planet’s gravity is constantly tugging on its siblings, disrupting their perfect orbits and subtly altering the timing of when each one passes in front of the star. And since the strength of a planet’s gravity is related to its mass, by measuring all those little variations, astronomers can work out their masses much more accurately. That technique could actually help clarify another surprise, too.

See, unlike in our solar system, the planets around TOI-178 seem to be kind of randomly arranged — with fluffy gas planets mixed in with dense, rocky ones. The researchers aren’t sure how that could happen, but knowing the masses of these worlds will at least help them confirm what types of planets they’re looking at. And then, the system could be an important target for research simulations to study more.

Because like on Venus, every time we find something unexpected, it usually means there’s more research to come. Thanks for watching this video, and thanks especially to all of our patrons! Thank you for your support, your curiosity, and for making all of this possible.

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