Are there many planets with life?

After the Pentagon revealed hundreds of reports of unidentified aerial phenomena.

We know that one in five stars has a planet similar to Earth. There are 200 billion stars in our galaxy alone, explains Lisa Kaltenegger, an astrobiologist at Cornell University. That means there are a 40 billion chance that planets similar to ours exist .

NASA's James Webb Space Telescope.

I'm a member of the Near Infrared Imager and Gapless Spectrograph (NIRISS) team , one of the instruments on the James Webb Space Telescope. We're currently looking at the Trappist-1 system, along with these rocky worlds that are in the habitable zone. So some of these worlds could harbor life.

Right now, we're focusing on gases (things that are inhaled and exhaled). If you see something unusual on one of these planets – like smudges on the ground – it could be life. So we use telescopes to look for life. You have to be very careful when looking for signs of life, because it's entirely possible that there's a geology that's different from ours and you don't know about it.

Life on Earth needs water, but water alone is not enough. Hopefully we will find oxygen, but oxygen alone is not enough. We also want to find methane. This is why I created a model of the Earth from the beginning, to determine how long it would take for traces of life to be visible. No one has ever tried that. How long would you expect the Earth to be habitable? We came up with 2 billion years, because that's how long it would take for the combination of oxygen and methane to act in the atmosphere on this planet.

So we're on the cusp of being able to detect life in the universe because for the first time, we know that there are a lot of planets out there and we know where the nearest ones are. We also know that on a planet like Earth, over the course of about 2 billion years, you have to look at both the air and the atmosphere.

With the James Webb Space Telescope, a space observatory designed to detect infrared radiation from objects in the solar system, we can only observe the atmosphere of a planet passing between us and its star, from which the light from the star will be filtered through the atmosphere of that planet.

That light reaches my telescope after it has been filtered through the planet's atmosphere. The molecules that light hits are all made differently; they require different amounts of energy - different colors of light - to vibrate and spin, so by looking at which color is missing, I can tell you what's in that planet's atmosphere. I can't see the surface of the planet, because if light were to hit the surface, it would reflect back and not go straight through my telescope. So for now, we're limited to looking for gases.

The next generation of telescopes we are designing – called the Habitable Worlds Observatory – is larger than James Webb and the missions for it are planned for around 2035/2040. After that, we want to learn more about the planets, about their surfaces, about the colours we can see and then compile the evidence.

Two Trappist-1 exoplanets pass in front of their star (Illustration).

When you look at the evolution of the Earth, the more oxygen we have, the more abundant life has evolved. So if we find a planet with 30% oxygen, like the time of the dinosaurs, large or complex organisms could exist. It would be an incredible discovery and I believe that humanity would consider this its greatest adventure. The scientific community is spread out all over the world and scientists are closely connected - countries would pool their resources to build a really large telescope.

If another civilization finds us, hypothetically, they could be a hundred light years away. And the question is: Why don't they come here? Well, I don't know if we're that interesting. I love Earth, but it's ridiculous to assume that everyone will immediately want to visit and talk to us.

I think that by trying to find life or other Earth-like planets, everything we learn out there will help us understand our own planet and protect it better. I think we will discover a habitable planet in the near future, which is why I am working so hard to try to make this happen. And so are many others.

Everyone was hopeful that what we found in the Trappist-1 system might mean something, that this was actually the first sign of an interesting biochemical process that might imply life. We were all excited because for the first time in history, we had the tools and the ability to explore that.