Astronomers Release a Huge Survey of Exocomet Belts

The study of exoplanets is challenging enough with the immense distances and glare from the host start but astronomers have taken planetary system explorations to the next level. A team of astronomers have recently announced that they have observed belts of icy pebbles in systems with exoplanets. Using a radio telescope they have been able to detect wavelengths of radiation emitted by millimeter-sized pebbles created by exocomet collisions! Based upon this survey, they have found that about 20% of planetary systems contain these exocometary belts.

Our own Solar System is peppered with them so it’s perfectly reasonable to expect to find them in planetary systems around other stars. The so called exocomets are generally only detected when they pass through or near to our own system. It would also be reasonable to assume they are made of the same icy and rocky material as our own comets but they can still provide valuable insights into the formation and evolution of exoplanetary systems. The first such comet was discovered around the star Beta Pictoris in the 19080s.

A team of astronomers that have been working upon the REASONS (REsolved ALMA and SMA Observations of Nearby Stars) study and have imaged exocomet belts around nearby stars! ALMA (the Atacama Large Millimeter/submillimeter Array) and SMA (Submillimeter Array) are powerful radio observatories that explore the skies in millimetre and submillimeter wavelengths. ALMA is based in northern Chile and composed of an array of 66 dishes and SMA is in Hawaii consisting of 8 dishes. 

The team led by astrophysicists from Trinity College Dublin have been revealed images that reveals pebbles and hence the locations of exocomets. In most cases, they are located tens to hundreds of astronomical units from their host star (one astronomical unit is the average distance from Earth to the Sun.) At theses immense distances from the star the temperatures will be in the between -250 and -150 degrees where any water will be frozen. The observations have detected the radiation emitted from the exocometary collisions. It’s the first time such an in depth analysis has been completed and to date, they have released images from belts in 74 exoplanetary systems. 

The rings are quite varied with some multiple disks and risks, others exhibiting high eccentricity. The eccentricity suggests that there are planets in these systems causing gravitational effects to modify the distribution of the pebbles in the belts.

Co-author of the study Dr Sebastian Marino,  Royal Society University Research Fellow from the University of Exeter explained “The images reveal a remarkable diversity in the structure of belts. Some are narrow rings, as in the canonical picture of a ‘belt’ like our Solar System’s Edgeworth-Kuiper belt. But a larger number of them are wide, and probably better described as ‘disks’ rather than rings.”

The study was able to develop a model showing that the number of pebbles seems to decrease for older planetary systems. This makes sense since an aged system will have run out of exocomets to generate the debris. They also found that the decrease in pebbles is faster when the belt is closer to the star.

Over the last few decades the focus seems to have been on exoplanets but this recent study has shown that the field of exocometary research is well and truly off the starting blocks and revealing fascinating insights into the exoplanetary systems. 

Source : Astrophysicists reveal structure of 74 exocomet belts orbiting nearby stars in landmark survey

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