Astronomers Discover Exocometary Belts around 74 Stars | Sci.News
Astronomers have imaged planetesimal belts in 74 planetary systems as part of the REsolved ALMA and SMA Observations of Nearby Stars (REASONS) survey.
This gallery contains 74 images of different star systems with exocometary belts taken with the Submillimeter Array (SMA) and the Atacama Large Millimeter/submillimeter (ALMA) radio telescope facilities. Image credit: Luca Matrà.
To find evidence for comets outside our Solar System, astronomers turned to two facilities that detect particular bands of radio waves: the Submillimeter Array (SMA) and the Atacama Large Millimeter/submillimeter Array (ALMA).
Because of the size of the dust and rocks in these belts, this type of light is particularly good at finding and imaging these structures.
The stars in the study ranged in ages from very young to middle-aged like our Sun.
“A joint program between SMA and ALMA dubbed REASONS marks a significant milestone in the study of exocometary belts because its images and subsequent analysis reveal where the pebbles and the exocomets are located,” said Trinity College Dublin astronomer Luca Matrà and colleagues.
“In these regions, it is so cold (minus 250 to minus 150 degrees Celsius) that most compounds including water are frozen as ice on these exocomets.”
“Exocomets are boulders of rock and ice, at least a kilometer in size, which smash together within these belts to produce the pebbles that we observe here with the ALMA and SMA arrays of telescopes,” Dr. Matrà said.
“Exocometary belts are found in at least 20% of planetary systems, including our own Solar System.”
“The Kuiper Belt is an example of a cometary belt in our own Solar System.”
“Located far beyond the orbit of Pluto, some scientists think the Kuiper Belt is the source of water for the inner Solar System where Earth is located, delivered through comets billions of years ago.”
The new images show a remarkable diversity of structure in the belts. Some are narrow rings, while others are wider and could be categorized more as disks than belts.
Moreover, some of the 74 exocomet systems have multiple rings or disks and some of those are eccentric, meaning not a circular orbit but more like an oval.
This provides evidence that yet undetectable planets or perhaps moons are present and their gravity affects the distribution of pebbles in these systems.
“Arrays like the ALMA and SMA used in this work are extraordinary tools that are continuing to give us incredible new insights into the universe and its workings,” said Dr. David Wilner, an astrophysicist at the Harvard & Smithsonian’s Center for Astrophysics.
“The REASONS survey required a large community effort and has an incredible legacy value, with multiple potential pathways for future investigation.”
“The REASONS dataset of belt and planetary system properties will enable studies of the birth and evolution of these belts, as well as follow-up observations across the wavelength range, from the NASA/ESA/CSA James Webb Space Telescope to the next generation of Extremely Large Telescopes and upcoming ALMA’s plans to zoom even further into the details of these belts.”
A paper describing the results was published in the journal Astronomy & Astrophysics.
_____
L. Matrà et al. 2025. REsolved ALMA and SMA Observations of Nearby Stars (REASONS): A population of 74 resolved planetesimal belts at millimetre wavelengths. A&A 693, A151; doi: 10.1051/0004-6361/202451397
