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Cold bands of dust surround the closest star to our Solar System — and maybe more planets

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Proxima Centauri is a complex place

An artist rendering of the dust bands around Proxima Centauri
Image: ESO/M. Kornmesser

Proxima Centauri, the nearest star to our Solar System, may not have just one planet orbiting around it; the star may host a whole complex planetary system. Astronomers have detected belts of cold dust surrounding Proxima Centauri, indicating that the star is home to many more objects — such as rocks the size of asteroids and even more planets that we haven’t seen yet.

That would mean another complex planetary system is right next door to us — cosmically speaking. Located just over 4 light-years from Earth, Proxima Centauri is the closest star to Earth apart from the Sun. Last year, astronomers discovered that a planet roughly the size of Earth orbits around Proxima Centauri, and it’s located within the star’s habitable zone — the area where temperatures are just right for water to pool on a planet’s surface. That makes the world a prime candidate for studying and even visiting, if we ever send a probe to another star someday.

But astronomers have wondered if there is even more to discover around Proxima Centauri. Using the ALMA telescope in Chile, a team of researchers wanted to see if they could detect bands of debris, similar to the bands in our Solar System like the asteroid belt between Mars and Jupiter or the Kuiper Belt that orbits beyond Neptune. These bands of objects are thought to be leftover remnants from when the Solar System formed 4.5 billion years ago that didn’t form into planets. And the astronomers thought comparable bands might be around Proxima Centauri too.

“So we think that whenever there is a planet around a star, there’s going to be some kind of asteroid belt as well,” Enrique Macías, an astronomer at Boston University and one of the members of the study team, tells The Verge. “It’s just debris from the formation of the system. That’s what we were looking for.”

Proxima Centauri in the sky, along with Alpha Centauri A and B — the two other stars in the system.
Image: Digitized Sky Survey 2, Davide De Martin/Mahdi Zamani

When observing Proxima Centauri, ALMA detected emissions from a dust band that extends hundreds of millions of miles out from the star. The combined mass of all of the material in the belt is about one-hundredth that of Earth’s, and the band is incredibly cold, around -382 degrees Fahrenheit (-230 degrees Celsius). The findings are to be detailed in the Astrophysical Journal Letters.

And it’s possible that’s not the only band around Proxima Centauri. “There seems to be not just one belt, but more than one,” says Macías. “Maybe even three regions of dust.” Data from ALMA indicates there may be two other bands farther out, but more observations are needed to confirm that they exist.

Finding another complex planetary system so close by may mean that our galaxy is filled with complex systems like our own. Plus this discovery just makes the Proxima Centauri system even more tantalizing to researchers. Experts have already proposed a campaign called Breakthrough Starshot, which involves propelling a tiny spacecraft to the Proxima Centauri system using lasers. Now, it seems possible that astronomers will be finding more planets in this star system to study in the future. With so much leftover material around Proxima Centauri that didn’t form into planets, it’s possible that some of this material did become planets that just haven’t been found yet. “Our observation seem to indicate there are going to be more planets, because we see a lot of complexity,” says Macías. “In the close future we’re going to detect other planets in the system for sure.”