Astrophysicists have successfully captured images of numerous exocomet belts surrounding nearby stars, along with the tiny pebbles found within them. These sharp images show light being emitted from millimeter-sized pebbles orbiting 74 stars of various ages — from newly formed stars to those in more developed systems like our Solar System.
For the first time, a team of astrophysicists from Trinity College Dublin has managed to image many exocomet belts around nearby stars, including the small pebbles nestled within them. These high-quality images reveal light emitted from tiny millimeter-sized pebbles in the belts orbiting 74 nearby stars, which vary significantly in age, from those that are just forming to more established systems like our Solar System.
The REASONS (REsolved ALMA and SMA Observations of Nearby Stars) study is a groundbreaking achievement in exocometary belt research. The images and analyses provide insights into the positioning of the pebbles and exocomets, typically located tens to hundreds of astronomical units (au) from their central star.
In these chilly regions, temperatures range between -250 and -150 degrees Celsius, allowing compounds such as water to freeze into ice on these exocomets. Therefore, the astrophysicists are identifying the locations of ice reservoirs within these planetary systems. REASONS is the first project to reveal the structure of these belts across a substantial sample of 74 exoplanetary systems.
The Atacama Large Millimeter/submillimeter Array (ALMA) consists of 66 radio telescopes located in the Atacama Desert in northern Chile, while the Submillimeter Array (SMA) is an eight-element array based in Hawaii. Both observatories focus on electromagnetic radiation across millimeter and submillimeter wavelengths. This study employed both ALMA and SMA to create images that enhance our understanding of exocomets like never before.
“Exocomets are large icy and rocky boulders, each at least 1 km wide, that collide within these belts to form the pebbles observed by the ALMA and SMA telescopes. Remarkably, exocometary belts exist in at least 20% of planetary systems, including our own,” stated Luca Matrà , Associate Professor in Trinity’s School of Physics and the lead author of the recently published research article in the journal Astronomy and Astrophysics.
Coauthor Dr. Sebastián Marino, a Royal Society University Research Fellow at the University of Exeter, remarked: “The images show a fascinating variety in the structures of these belts. Some are narrow rings, similar to the familiar image of a ‘belt’ like the Edgeworth-Kuiper belt in our Solar System, while most appear as wide disks rather than simple rings.”
Some systems feature multiple rings or disks, with some showing eccentric shapes, offering evidence of yet-undetected planets whose gravitational pull affects the arrangement of pebbles within these systems.
Prof. Matrà explained, “A comprehensive study like REASONS reveals broad population properties and trends.”
“For instance, the study confirmed that the population of pebbles declines as planetary systems age, as belts exhaust larger exocomets that shatter to form them. It also demonstrated for the first time that this decline in pebbles occurs more rapidly closer to the central star. Furthermore, the belts’ vertical thickness indirectly suggests the presence of unseen objects ranging from 140 km to Moon-sized.”
Dr. David Wilner, a Senior Astrophysicist at the Center for Astrophysics | Harvard & Smithsonian, emphasized, “Instruments like ALMA and SMA are extraordinary tools continuing to provide remarkable new insights into the universe and its dynamics. The REASONS survey represents a significant collaborative effort and offers substantial legacy value, paving the way for numerous future investigative paths.”
“For instance, the REASONS dataset detailing belt and planetary system characteristics will facilitate research on the formation and development of these belts, along with ongoing observations spanning across various wavelengths, from the JWST to the next generation of Extremely Large Telescopes and ALMA’s upcoming ARKS Large Program to delve even deeper into the specifics of these belts.”
