Since the confirmation of the first exoplanets in the mid-1990s, a small armada of telescopes, orbiters and probes has identified at least 3,300 confirmed planets outside our own neighborhood—some of which are Earth-sized and exist in a habitable zone. Seven orbit just one star in the TRAPPIST-1 system.
Last year, the hunt heated up when astronomers announced the discovery of an Earth-sized planet in the habitable zone of our nearest stellar neighbor, Proxima Centauri, just 4.33 light years away. Dubbed Proxima b, it was eventually determined that the planet likely can’t support life. But a new study raises hope that other planets may still lurk around the star, reports Ryan F. Mandelbaum at Gizmodo.
Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile examined the light coming from Proxima Centauri, focusing in on the infrared and microwave wavelengths. What they found is a cold ring of dust encircles the star one to four times the distance Earth is from the Sun. The data hints that there may be two more dust belts, much farther away from the star—lying at a distance similar to our own solar system’s Kuiper Belt. But more data is needed to draw definitive conclusions about those regions. The research appears in the The Astrophysical Journal Letters.
While ALMA did not detect any planets directly, the debris belts are believed to be a good sign that more planets besides Proxima b might orbit the star. “So we think that whenever there is a planet around a star, there’s going to be some kind of asteroid belt as well,” Boston University astronomer and co-author Enrique Macías tells Loren Grush at The Verge. “It’s just debris from the formation of the system. That’s what we were looking for.”
Even though Proxima Centauri is right next door, in the celestial sense, it’s still difficult to find any planets orbiting the star. That’s because researchers often find exoplanets by looking for a tiny wobble in a star’s light, something that can be measured if the star can be clearly seen. But as a small red dwarf with faint light, Proxima Centauri is a difficult candidate for a planet hunt, even if it is relatively close. As Megan Gannon at Space.com reports, it took a consortium of 30 researchers systematically observing the star in a project called the “Pale Red Dot” campaign to eventually detect Proxima b orbiting the star.
The latest ALMA data is adding to the hard-won picture emerging of the Proxima Centauri system, and there is some preliminary data to suggest the presence of at least one planet hiding in the ring of dust and debris, co-author Guillem Anglada-Escudé of Queen Mary University of London tells Mandelbaum. But more work is necessary for confirmation of this or any other planets.
“This time we could only get the first snapshot,” he says. “We want to get more ALMA time to get higher resolution images of these dust rings and see what they really are.”
While it’s still too early to tell if they will find any more planets around the red dwarf, other researchers are preparing to explore whatever is there. Proxima Centauri is part of a trio of stars, which also includes Alpha Centauri A and Alpha Centrauri B, that are the focus of the project Breakthrough Starshot. Sponsored by Russian billionaire physicist Yuri Milner, the project is focused on the development of a feasible but technically challenging plan to send a swarm of nano spacecraft to the system to explore, including a fly-by of Proxima b. This newest discovery hints that they might have something to write home about.