Astronomers discover the largest collection of comets outside the solar system
Astronomers have detected 74 exocomet belts around nearby stars, revealing their role in planet formation. The discovery, made with ALMA and SMA, suggests that these bodies could influence the evolution of star systems, similar to the Kuiper Belt in our solar system.
An international team of astronomers has achieved an unprecedented feat: obtaining images of dozens of exocomet belts orbiting around 74 nearby stars . This discovery, published in the journal Astronomy & Astrophysics , offers new clues about the formation of stars and planetary systems in the universe.
Exocomets, similar to comets in our solar system, are fragments of rock and ice found in extremely cold regions, with temperatures between -250 and -150 °C.
They are thought to play a key role in the evolution of star systems , transporting key elements such as water to forming planets.
An unprecedented discovery
To detect these comet belts outside the solar system, astronomers turned to two of the world's most advanced radio telescopes: the Atacama Large Millimeter/submillimeter Array (ALMA), located in Chile, and the Submillimeter Array (SMA), located in Hawaii. Both instruments are capable of capturing radio waves emitted by the dust and fragments of these celestial bodies, allowing them to reconstruct detailed images of their structures.
This work was carried out within the framework of the REASONS ( REsolved ALMA and SMA Observations of Nearby Stars ) programme, a collaborative effort that has provided the most complete picture to date of exocomet belts around other stars.
According to the researchers, at least 20% of the planetary systems studied host these comet belts , suggesting that they could be a common feature in the evolution of planets.
A window into the past of our own solar system
One of the most interesting aspects of the study is its similarity to our own solar system. Scientists have compared these belts to the Kuiper Belt , a vast region of icy bodies located beyond the orbit of Pluto.
Some experts believe that the Kuiper Belt played a crucial role in Earth's early history, supplying water through cometary impacts . If exocomets detected in other systems function in a similar way, they could be influencing the formation and evolution of habitable planets in the universe.
Diversity of structures and clues about invisible planets
Analysis of the 74 systems detected revealed a great diversity in the structure of exocomet belts . Some have narrow, well-defined rings, while others are broader and more diffuse, taking on more disk-like shapes.
In addition, astronomers identified systems with multiple belts, as well as structures with eccentric orbits, i.e. not perfectly circular . These irregularities suggest the possible presence of as yet undetected planets, or even moons, whose gravitational influence alters the distribution of comets within the belts.
“The ALMA and SMA observations continue to give us surprising insights into the nature of the universe and how these systems work ,” said David Wilner, an astrophysicist at the Smithsonian Astrophysical Observatory and co-author of the study.
A legacy for the exploration of the cosmos
The catalogue of images and data collected by the REASONS programme will serve as a basis for future studies on planet formation and the evolution of exocomet belts . Astronomers plan to conduct further observations with the James Webb Space Telescope (JWST) and the upcoming Extremely Large Telescopes , which will allow for even more detailed analysis of these enigmatic systems .
In addition, ALMA has plans for improvements in the coming years that will allow for further study of these belts , opening up new possibilities for the detection of planets in formation and the understanding of the role of exocomets in the chemistry of planetary systems.
This discovery marks a milestone in modern astronomy and reinforces the idea that the processes that shaped our own solar system could be occurring in other corners of the universe, providing crucial clues in the search for life beyond Earth.
News reference:
L. Matrà et al, REsolved ALMA and SMA Observations of Nearby Stars (REASONS): A population of 74 resolved planetesimal belts at millimeter wavelengths , Astronomy & Astrophysics (2024). DOI: 10.1051/0004-6361/202451397