Free Astronomy Magazine March-April 2026

35 MARCH-APRIL 2026 ASTRO PUBLISHING saw the impact of mas- sive objects around the star. The Fomalhaut system appears to be in a dynamical up- heaval, similar to what our Solar System expe- rienced in its first few hundred million years after formation. “This is certainly the first time I’ve ever seen a point of light appear out of nowhere in an exoplanetary system,” said principal investiga- tor Paul Kalas of the University of California, Berkeley. “It’s absent in all of our previous Hubble images, which means that we just wit- nessed a violent colli- sion between two massive objects and a huge debris cloud unlike any- thing in our own Solar System today. Amazing!” Just 25 light-years from Earth, Fomalhaut is one of the brightest stars in the night sky. Lo- cated in the constellation Piscis Aus- trinus, also known as the Southern Fish, it is more massive and brighter than the Sun and is encircled by sev- eral belts of dusty debris. In 2008, scientists used Hubble to discover a candidate planet around Fomalhaut, making it the first stellar system with a possible planet found using visible light. That object, called Fo- malhaut b, now appears to be a dust cloud masquerading as a planet – the result of colliding planetesimals. While searching for Fomalhaut b in recent Hubble observations, scien- tists were surprised to find a second point of light at a similar location around the star. They call this object “circumstellar source 2” or “cs2” while the first object is now known as “cs1.” Why astronomers are see- ing both of these debris clouds so physically close to each other is a T his artist’s concept shows the sequence of events leading up to the creation of dust cloud cs2 around the star Fomalhaut. [NASA, ESA, STScI, R. Crawford (STScI)] ! most impossible to get by any other means,” said co-author Mark Wyatt at the University of Cambridge in England. “Our estimates put the planetesimals that were destroyed to create cs1 and cs2 at just 30 km in size, and we infer that there are 300 million such objects orbiting in the Fomalhaut system.” “The system is a natural laboratory to probe how planetesimals behave when undergoing collisions, which in turn tells us about what they are made of and how they formed,” ex- plained Mark. The transient nature of Fomalhaut cs1 and cs2 poses chal- lenges for future space missions aim- ing to directly image exoplanets. Such telescopes may mistake dust clouds like cs1 and cs2 for actual planets. “Fomalhaut cs2 looks ex- actly like an extrasolar planet re- flecting starlight,” said Paul. “What we learned from studying cs1 is that a large dust cloud can masquerade as a planet for many years. This is a cautionary note for future missions that aim to detect extrasolar planets in reflected light.” mystery. If the collisions between as- teroids and planetesimals were ran- dom, cs1 and cs2 should appear by chance at unrelated locations. Yet, they are positioned intriguingly near each other along the inner portion of Fomalhaut’s outer debris disk. Another mystery is why scientists have witnessed these two events within such a short timeframe. “Previous theory suggested that there should be one collision every 100,000 years, or longer. Here, in 20 years, we’ve seen two,” explained Paul. “If you had a movie of the last 3000 years, and it was sped up so that every year was a fraction of a second, imagine how many flashes you’d see over that time. Fomal- haut’s planetary system would be sparkling with these collisions.” Col- lisions are fundamental to the evo- lution of planetary systems, but they are rare and difficult to study. “The exciting aspect of this observation is that it allows researchers to estimate both the size of the colliding bodies and how many of them there are in the disk, information which is al-