This University of Arizona professor is excited about the possibility of life on a nearby planet

The stellar system closest to our sun appears to be the home of a planet. It’s in the Alpha Centauri system, just four light years away from us. And if the planet turns out to be real, it’d mean there’s a planet in what’s known as the habitable zone of the closest star. And that could have implications for the possibility of life.

Kevin Wagner first got a hint of this planet a few years ago, but new observations from the James Webb Space Telescope have him even more excited.

Wagner is an assistant research professor at the University of Arizona, where he says in its simplest terms, he takes pictures of planets around nearby stars.

Full conversation

KEVIN WAGNER: So, we're talking about the deepest images of the closest Sun-like star. And by deep I mean we're looking at a very bright star and any planets around it are going to be fainter points of light. So, the depth of the observation is the faintness of the point of light that we're able to see next to it.

So, we're pushing down towards not quite Earth-like planets, but definitely into the regime of giant planets. So if there's a Jupiter-like planet in an Earth-like orbit, that's what we're able to see is a faint point of light right next to this very bright star. And the difference in brightness there is something like 1 to 1 million.

MARK BRODIE: And where exactly is this relative to where we are here on Earth?

WAGNER: So Alpha Centauri is the closest stellar system to us. It's a system of three stars, Alpha Centauri A and B. And then they're orbited by a red dwarf star called Proxima.

BRODIE: And why is this so potentially interesting to you?

WAGNER: Well, it's interesting for a number of reasons. One being the closest stellar system to us, any planets around it — once we identified them — are ones that we'll be able to study in the most amount of detail. Also being the closest star, we can think about sending robotic probes there in the not-too-distant future and to get really exquisite data on these systems.

Beyond that, I think this is the most logical stepping stone for humanity as we progress out into the galaxy. It's a factor of three closer than the next closest Sun-like star. So, it's just the logical place to go. And if it has a habitable planet or a habitable moon around a giant planet, then that makes it all the more exciting.

Michael Miller

BRODIE: Let me ask you about the habitability because it seems as though we have no idea really what's there now. But it seems as though the conditions are right for potentially life to exist, whether or not it does. Like I said, we don't know how significant it is that this is in sort of what scientists call the habitable zone, where life could theoretically exist.

WAGNER: So I'd say it's quite significant and very exciting. We're still just talking about a candidate planet. So the planet itself needs to be confirmed, and then we can go and look for rocky moons that might be orbiting it. And that would be the exciting environment for which we would look for life then.

BRODIE: Why would that be the exciting part?

WAGNER: Well, life as we know it needs a surface. We could possibly imagine, and people like Carl Sagan have imagined in the past, there being sort of atmospheric life beings in the atmosphere of a giant planet. But if we're talking about looking for life like we know it on Earth, then we're talking about life on the surface of a rocky planet or a rocky moon. And likely rocky body that has liquid water on its surface.

BRODIE: And am I right that the planet that you are looking at now, the assumption is that it is a gas planet, not, not a rocky surface planet?

WAGNER: Right. So we get that measurement from the brightness. What we measure is really just brightness in the image, and then we compare that to planetary brightness models. And these largely depend on the planet's radius and its temperature. The temperature we have a fairly good understanding of from the separation of the planet candidate from the star.

So with the temperature essentially set, then we're left with a measurement of radius. And that places it at about the radius of Jupiter.

BRODIE: How important has the James Webb Space Telescope been to getting to this information?

WAGNER: Well, it's very important. It's the only telescope that exists that can do this right now. The planet candidate was initially seen from the ground, but it was a really sort of one-off experiment that took over one of the biggest telescopes on Earth for a whole month and just stared at the brightest star in the sky for as much clearer observing time as we could get for a month.

That hasn't been done again and probably won't be done at that scale again in the future since — well, there's only really one closest star that you can do it for. But Webb is opening up additional views of that closest star in less time than — well, it doesn't take a month to get the same sort of detection with Webb. We can do it just in a bit over a day. And then it also opens up other stars.

BRODIE: So, how then do you plan to go about continuing to study and research this?

WAGNER: So, for this planet candidate, the next steps is to — the obvious next step is to get another observation with Webb. So we have the one detection from the ground, and we have the one detection with Webb. And then we also have two non-detections with Webb. Which basically just tell us that if this is a planet, then there's only so much space in the image where we wouldn't have seen it. And that's basically when it's too close to the star.

So, from these two detections and two non-detections, we can place constraints on the planet's orbit. And from those orbital constraints, we can predict where it will be again in the future. And then if we point Webb at Alpha Centauri again about a year from now, then we have a very strong prediction for where the planet should be and that we should be able to see it.

And then if we see it in that spot, then that would be rock-solid confirmation. And then we can think about things like studying its spectra for possible signs of atmospheric life, or looking for exomoons around it and all sorts of other interesting possibilities.

BRODIE: Is it a possibility to potentially send something to get closer and really get more detailed looks and maybe even measurements of particular aspects of this planet candidate at some point?

WAGNER: That's an aspect of this, that is unique to Alpha Centauri, that we can actually envision going there. And by going there, I mean, at first, tiny robotic spacecraft. Things that are on the scale of grams, that have likely the means of propulsion that are going to get these crafts, there would be lasers.

They could get to a fraction of the speed of light. And then being only four light years away, if you're traveling at the fraction of the speed of light, this is something that we can envision happening within just a matter of decades.

BRODIE: So, you have been quoted as calling this one of the most exciting results in astronomy of the decade. And I'm curious what leads you to say that?

WAGNER: Well, I don't think it's quite there yet, but I think it's shaping up to be. If this planet were confirmed as an actual planet in the habitable zone of the closest star, then I think it would qualify as one of the most exciting results of the decade. And in particular, because it would almost certainly have moons.

Almost every planet in the solar system has moons. Jupiter has multiple moons. Many of them, if they weren't orbiting Jupiter, but were orbiting the Sun, we would call them planets in their own right. So, I think it would be more surprising if a giant planet doesn't have moons than if it did. So, if this planet is real, then I think it very likely has moons, and those moons would also be in the habitable zone.

And that just opens up so many possibilities for astrobiology, for even the possible future of human civilization.