JOAN CARTAN-HANSEN, HOST: Astronomers have an amazing tool in the search for life on exoplanets.

It's the James Webb Space Telescope.

But what are they looking for and what can the James Webb Space Telescope do or not do in that search?

Let's find out.

(MUSIC) JOAN CARTAN-HANSEN, HOST: On December 25, 2021, astronomers launched the James Webb Space Telescope or JWST.

Scientists from NASA, the European Space Agency and the Canadian space agency spent 20 years building this state-of-the-art explorer.

The JWST is an infrared telescope.

Infrared light are light waves we can't see but we can feel as heat.

Some of the sun's heat comes from infrared light waves.

Your television remote operates with infrared light.

And exoplanets give off infrared light.

NASA observatory project scientist Michael McElwain says the JWST can learn a lot about an exoplanet using the transit method.

The transit method is used when a planet passes between the star and the observer.

The light of the star dims a tiny amount.

And that change in light indicates a possible exoplanet.

MICHAEL MCELWAIN: With transits, we'll actually be studying the atmospheres of these planets.

We now know of over 5,000 exoplanets.

But we, we actually know very little about the vast majority of these exoplanets.

We know that their, their masses, maybe their sizes, how long it takes for them to go and orbit around the star, that their, their host star.

But we, we don't really have a good idea about many of their compositions.

CARTAN-HANSEN: And that's where the James Webb Space Telescope can help.

MCELWAIN: We'll be studying their infrared, um, atmospheric properties, which really tells us a lot about their compositions, will tell us how these planets formed and evolved.

CARTAN-HANSEN: Astronomers use JWST to look for different molecules in an exoplanet's atmosphere.

MCELWAIN: We actually saw water in the atmosphere of Wasps 96 b., that was a, about a Jupiter size planet, but it was about half the mass of Jupiter.

And unlike Jupiter, um, which is very far away from the Sun, this is really close.

Very hot.

But, Webb and infrared is also able to search for, for methane and carbon dioxide, and that really gives us more insight as to what the atmospheric, um, temperatures are and where those planets formed.

CARTAN-HANSEN: So, what are astronomers looking for when they're looking for life on an exoplanet?

First, is the planet in the habitable zone?

When an exoplanet's orbit around its sun is far enough away that the exoplanet's atmosphere isn't too hot and the orbit isn't so far away that the atmosphere is too cold, that's when the exoplanet is in what's called the goldilocks zone or the habitable zone.

Next, astronomers analyze the exoplanets atmosphere.

The James Webb Space Telescope is good at studying the molecules found in exoplanets' atmospheres but may not be so good at detecting biosignatures.

Biosignatures are what astronomers think are signs of life, things like water vapor and oxygen.

But exoplanets the size of earth are small, and their atmospheres are even smaller, so JWST has a difficult time detecting them.

And astronomers themselves are still learning what biosignatures are and what they mean.

MCELWAIN: we don't expect to be able to actually detect biosignatures with Webb, but rather we'll be able to test whether or not these planets, have water, are conducive to having water on the surface that we think is a prerequisite for life.

CARTAN-HANSEN: Finding life.

If you think about it, that's a pretty amazing goal.

MCELWAIN: For a long time we thought, um, the Earth was at the center of the universe <laugh>, and then we sort of learned that the Earth is now going in orbit around the Sun.

There are other planets in our solar system.

We thought, you know, our, our solar system is totally unique.

But then back in 1995, we discovered planets orbiting other sunlight stars.

And so, we're no longer so unique.

And we're really, you know, I think as humans, we're really just explorers and trying to understand our universe and, and where we are and, and what we're doing here.

We're answering really big questions like, how does the universe work?

How do we get here?

What's our place in space?

Right?

And so, it's been a lot of fun.

I think I have the best job in the world, <laugh>.

I mean, it's, it's just amazing to be part of this, JWST mission, on the, the forefront of science.

If you want to learn more about exoplanets, check out the Science Trek website.

You'll find it at ScienceTrek.org.

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