Just 4.3 light years from Earth lies a star called Alpha Centauri A, which is famous for being the nearest star that resembles our own Sun.
In the popular Avatar movies, this star's system is home to a glowing fantasyland called Pandora, the made-up moon of an imaginary Jupiter-like planet.
It turns out that, in real life, a gas giant planet actually seems to be orbiting Alpha Centauri A, according to astronomers who peered at it with the James Webb Space Telescope.
What's more, the planet apparently orbits at a distance from the star where temperatures might be cozy enough for life, according to a pair of reports accepted by The Astrophysical Journal Letters.
And some scientists see no reason it couldn't have a moon, just like in Avatar.
"It probably does have moons," says Charles Beichman, an astronomer with Caltech and NASA's Jet Propulsion Laboratory.
Alpha Centauri A is part of a triple-star system, and has close companions known as Alpha Centauri B and Proxima Centauri. Together, they appear to be one of the brightest objects in the night sky, and have long loomed large in the imaginations of both scientists and science fiction authors.
"I mean, this goes back to books by Arthur C. Clarke to more recently, you know, the movie Avatar," he says. "Certainly in your science fiction dream, you say, 'Well, if we're going to get anywhere, we're going to be able to go to Alpha Centauri,'" given that it's right nearby in cosmic terms.
But even though scientists have been able to discover thousands of planets orbiting stars beyond our solar system in recent years, including some around Proxima Centauri, which is fairly a dim star, it's been difficult to go planet-hunting around Alpha Centauri A and B, which orbit each other.
Part of the problem, says Beichman, is that the gravitational interactions between these two stars complicate one common method for finding planets, which relies on detecting how the planets' gravity tugs on their host stars.
And then there's the fact that their starlight is so bright that it can overwhelm telescopes. It's just like if you tried to point your cellphone camera at a very bright object, says Beichman: "It just, you know, blurs everything out, or blasts everything out."
But the James Webb Space Telescope offered a couple of advantages. One of its instruments is designed to detect exactly the kind of infrared light that would come from a temperate planet. It also has "specially-designed masks" that block out the light of a central star "and let you see in close, to see if you can see a planet," Beichman explains.
He and his colleagues' first sighting of a planet around Alpha Centauri A happened about a year ago. They've tried to observe it since then, but its orbit may have taken it to a spot where it's hidden from the telescope's view. Because its presence still needs to be confirmed with more observations, for now it's considered just a candidate planet.
From what they can tell, though, it looks to have the right size and mass to be a gas giant.
"It's something like a Saturn mass, a Jupiter radius, and just like the gas giant planets in our own solar system, if you move them in closer," says Beichman, who adds that the planet conceivably could even have rings.
Temperatures might be in the range of 40 to 50 degrees below zero Fahrenheit, making this "in the outer edge of the habitable zone," he says, but it could have periods that are warmer, given that it seems to have an eccentric orbit that would bring it closer to its star at times.
And while a gas giant planet seems an unlikely home for life, moons offer the possibility of solid ground, or even oceans.
"I would expect that there are probably moons there. Moon formation around giant planets generally should be quite common," says Mary Anne Limbach, an astronomer at the University of Michigan who has searched for alien moons but wasn't part of the team of researchers working on this planet discovery.
She thinks this planet candidate might conceivably even have decently-large moons, like maybe the size of Mars, "in sort of an optimistic case."
"I think that's definitely an environment where you could get, potentially, life to evolve," she says, noting that even in our own solar system, many scientists see moons — such as Jupiter's icy moon Europa, or Saturn's hydrocarbon-rich Titan — as the best places to search for life beyond Earth.
Another veteran moon-hunter agreed that a decent-sized lunar satellite was possible in theory, though he was skeptical.
David Kipping, an astronomer with Columbia University, told NPR in an email that this planet candidate appears to be on the small side to expect a big moon. To him, something the size of Titan seems more likely.
"But Titan is too small to hold onto its atmosphere if we moved it into the habitable zone" around a star, he notes. That means to potentially have a life-supporting moon around this planet candidate, he says, "really you need this planet to have an unexpectedly big moon."
So could this star system have a Pandora, like in Avatar? "It's not impossible," says Kipping, but to him it seems like a bit of a stretch that would require a number of things to line up just right.
The question of whether a moon might exist that could have any life at all, however, is very different from the question of whether it could feature a lush, complex web of life-forms, like scifi writers dreamed up for Avatar's Pandora, points out Limbach.
She says that while researchers have found signs of moons outside our solar system, these moon detections haven't been confirmed to be real, just like this putative new gas giant planet still isn't nailed down for sure.
"I think the first thing I want to see before we claim victory and say this is a planet," says Limbach, "is follow-up observations to confirm it."
Still, she adds, "I think it's really exciting that our neighbor could have a giant planet, so close by."
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