Astronomers have detected at least one cold dust belt surrounding the closest star to the Sun, Proxima Centauri. The presence of such a feature suggests there might be more than one planet orbiting Proxima.
The star is a red dwarf much smaller and cooler than our Sun, and it is orbited by one known planet, Proxima b, that is Earth-sized and temperate. The observations, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), shows a ring of dust a few hundred million kilometers from the star, with hints in the data of another ring further out. This discovery is reported in the Astrophysical Journal Letters.
“The dust around Proxima is important because, following the discovery of the terrestrial planet Proxima b, it’s the first indication of the presence of an elaborate planetary system, and not just a single planet, around the star closest to our Sun,” lead author Guillem Anglada, from the Instituto de Astrofísica de Andalucía, said in a statement.
The dust belt is estimated to weigh around 1 percent of our planet and have a temperature of about -230°C (-382°F), which is similar to the temperature of the Kuiper Belt – a disc that's made mostly of icy bodies and dwarf planets beyond the orbit of Neptune.
The data also provides a glimpse of another much colder belt about 10 times further out than the newly discovered ones. This is the best evidence so far of multiple planets in the system. Proxima b is only 4 million kilometers (2.5 million miles) from the star, so it wouldn’t have the influence to shape dust belts so far out.
“This result suggests that Proxima Centauri may have a multiple planet system with a rich history of interactions that resulted in the formation of a dust belt," Anglada added. "Further study may also provide information that might point to the locations of as yet unidentified additional planets."
Understanding the Proxima Centauri system is extremely important. Researchers intend to send the first interstellar microprobe, the so-called project Breakthrough Starshot, there soon.
“These first results show that ALMA can detect dust structures orbiting around Proxima," added co-author Pedro Amado. "Further observations will give us a more detailed picture of Proxima's planetary system. In combination with the study of protoplanetary discs around young stars, many of the details of the processes that led to the formation of the Earth and the Solar System about 4600 million years ago will be unveiled. What we are seeing now is just the appetizer compared to what is coming!”