Proxima Centauri is the closest star to the sun, situated a mere 4.25 light-years away from our planet, in the Centaurus constellation. Other than the sun, it is our nearest star. Until now, it was believed the only planet orbiting this faint red dwarf was Proxima b, an Earth-sized temperate planet discovered just last year in the star’s habitable zone. Yet a more recent find uncovered not one, but two belts of cold dust surrounding Proxima Centauri, which hint at the possibility of “an elaborate planetary system” nearby that astronomers may not know about.
The ALMA Observatory in Chile took a close look at Proxima Centauri and eventually picked up a glowing cloud of cold dust around the star. This newly-discovered dust belt lies in a vast region of outer space extending for hundreds of millions of miles from the red dwarf. It stretches at distances that range between one and four astronomical units (AU) — one AU being the distance between Earth and the sun, namely about 93 million miles or 150 million kilometers.
The cold dust cloud swirling around Proxima Centauri is essentially made up of rock and ice particles of various sizes, ranging from less than a millimeter to several miles in diameter. It also boasts a combined mass of roughly 1 percent of our planet (fairly similar to the Kuiper Belt, located in the outer solar system beyond Neptune), shows a study on the recent discovery due to be published in the Astrophysical Journal Letters.
Such dust belts as the one seen encircling Proxima Centauri are thought to be ancient remnants from the birth of our solar system 4.5 billion years ago. Their composition is chiefly attributed to leftover materials that failed to amass and give rise to planets.
The dust belt revolving around Proxima Centauri is indubitably a cold place. Judging by the low luminosity of the red dwarf, researchers estimate the dust belt’s temperature to be nearly 40 degrees Kelvin (-382 degrees Fahrenheit or -230 degrees Celsius), also similar to that of the Kuiper Belt.
But wait, there’s more. Data from the ALMA Observatory indicates there could be another even cooler dust belt in the outer regions around Proxima Centauri, at a distance of about 30 AU from the star. Both dust belts are found farther away than the planet Proxima b, which resides about 2.5 million miles (or four million kilometers) away from its parent star.
Yet, what is remarkable about this find are the possibilities it entails. According to study author Guillem Anglada, from the Instituto de Astrofísica de Andalucía (CSIC) in Spain, Proxima b may not be the sole planet orbiting our second closest star. The ALMA observations suggest there could be other exoplanets hiding in the dust belt around the red dwarf, and which have so far gone undetected. In fact, there actually might be an entire planetary system right outside our cosmic doorstep, Anglada explains in a news release issued by the European Southern Observatory.
“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.”
Anglada believes further research could yield the position of “unidentified additional planets” in the Proxima Centauri system. In his opinion, the red dwarf harbors “a multiple planet system,” whose planets have long interacted with each other, resulting in cosmic debris that ultimately formed the dust belt around the star.
At the same time, co-author Pedro Amado, also from CSIC, says the discovery is merely the tip of the iceberg and represents “just the appetizer” in a series of forthcoming astronomic breakthroughs. Amado points out that future investigations — such as the Starshot project, which aims to explore the Proxima Centauri system with laser-propelled microprobes — could render not only a detailed image of the star’s planetary system but also a deeper understanding of how the Earth and our solar system were formed.
[Featured Image by Pete Draper/iStock]