'We Are Not Alone': How James Webb Telescope Is Hunting down Alien Worlds

In our vast universe containing unimaginably large numbers of stars and planets, scientists theorize that there surely must be some other life that has evolved elsewhere.

Thanks to the James Webb Space Telescope (JWST), we may be able to get one step closer to discovering the signs of our cosmic neighbors, on exoplanets many millions of miles away from home.

In a new PBS science series NOVA special called New Eye on the Universe, which premiered on February 22, scientists discuss how the JWST is helping them figure out which exoplanets have atmospheres, and therefore have a chance of having life on them.

"All common sense of looking at how biology, chemistry, geology and physics work, would say no, we're not alone," said Hakeem Oluseyi, an astrophysicist at George Mason University, in a clip from the documentary.

Exoplanets are planets orbiting stars other than our sun. We have found 5,332 confirmed exoplanets as of March 1, 2023, across 3,931 planetary systems. Some 855 of these star systems have more than one planet.

"There's many methods to detecting exoplanets," Néstor Espinoza, an astrophysicist and astronomer at the Space Telescope Science Institute (STScI) in Baltimore, told Newsweek.

"The most popular one, though, is the method of Transiting Exoplanet detection, in which we simply wait patiently until the planet passes in front of the stars. And if we're lucky enough, that transit happens in the same line of sight that we're looking from Earth, then we observe a little dimming of the flux that we observed from that star. And that's how we detect these kinds of exoplanets, as we call them. There's many other methods, but this one is by far the most popular one, the one from which most of the confirmed exoplanets to date have come from," he said.

Looking at exoplanets as they pass in front of their star also allows the astrophysicists to determine if the planet has an atmosphere, which would be a prerequisite for life on that planet.

"That comes from a very clever observation made back in 2000," Espinoza said. "They figured out that if a planet transits, then some of the starlight gets filtered through the atmosphere of the planet as the planet passes in front, the planet blocks part of the light, but this little fraction of the light that also goes through the atmosphere interacts with it. So some of that information is stored into that light."

The researchers can then analyze the light signals and determine if there are chemicals present that indicate there is an atmosphere, and if there is one, what it's made up of.

"There's two molecules that we're trying to answer that question [of if there is an atmosphere] from. One is carbon dioxide. And the reason why we're looking for carbon dioxide is based on our own Solar System experience. Mars and Venus have carbon dioxide dominated atmospheres. The earth is nitrogen, which means most of it is nitrogen. But it turns out that the carbon dioxide atmospheres produce the largest signals. So that's what we're looking [for] at first, trying to figure out if they have atmospheres. But people are also looking for water features," Espinoza said.

They also look for methane dominant atmospheres, which we also have in our own solar system, such as Titan, one of Saturn's moons.

Even if an exoplanet does have an atmosphere, that doesn't indicate that the planet will be habitable for life. The researchers need to analyze the contents of the atmosphere to see if there are any chemicals that are only created by living cells.

"There's no strong consensus on exactly what will claim or scream to you that that's life," Espinoza said. "You don't only need one molecule to be detected, you need several molecules that you can detect. If that chemistry could come from life, basically, the best example that I can give on that is like what has happened with Venus."

Espinoza described that when phosphine was detected on Venus, many claimed that this meant the planet had life, as usually phosphine is only produced by living creatures. However, after further research, scientists figured out that it is possible for phosphine to be created in the absence of life too

It is also possible that life elsewhere might be completely different to anything we can recognise, and that we might completely miss it because we're looking for the wrong signs.

"There's nothing to say that there could be other forms of life out there," Espinoza said. "But for us, it will be extremely hard to claim that that's life, what we would first say is that there's something funky in the data, right? It doesn't match our models, perhaps. That's another jump that I don't think we can make."

The JWST has been a "game-changer" for exoplanet research, as it has allowed astrophysicists a much greater degree of detail.

"But now with James Webb, you open up the amount of colors and regions, and colors equates to what kind of molecules you can detect. So we'd have all those like a tiny feature of water that you could see. But now with James Webb, you open up the whole chemical inventory, [it] can detect water, you can come to take carbon dioxide, and so on. So that really, it's a game changer in the precision, because the telescope is so large and so stable," he said. "The fact that we can not only explore this but explore it very precisely, is something that we have not accessed before."

Espinoza isn't holding his breath that the JWST will find life any time soon, but he remains open to the idea.

"Now in terms of the prospects of the James Webb Space Telescope detecting life, I don't think it's very likely, to be very honest. And I'm a good scientist, I'm putting the 'not very likely' warning. Because we don't know what we're going to be seeing in these data. But it will be good to keep in mind that the answer, I think, that the James Webb Space Telescope can really answer is: 'Does this planet have an atmosphere at all or not?' That's the very big question. That is one that is key. And it's like a small step for our students, but a huge step for mankind," he said.

"So we don't really know, we need data. We are at a start right now."

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