Young star systems are a place of violent collisions. Rocks, comets, asteroids and larger objects carom off one another and coalesce, gradually turning the primordial dust and ice of a stellar nebula into planets and moons. The largest of these collisions, however, are expected to be rare over the hundreds of millions of years it takes to form a planetary system — perhaps one every 100,000 years.

Now, astronomers have seen the aftermath of two powerful collisions within a 20-year period around a nearby star called Fomalhaut. These are either lucky observations or a sign that collisions are more frequent than predicted during planet formation.

The events — the first was detected in 2004 and the second in 2023 — are the first collisions between large objects directly imaged in any solar system outside our own.

“We just witnessed the collision of two planetesimals and the dust cloud that gets spewed out of that violent event, which begins reflecting light from the host star,” said Paul Kalas, adjunct professor of astronomy at the University of California, Berkeley, and first author of the report. “We do not directly see the two objects that crashed into each other, but we can spot the aftermath of this enormous impact.”

Over tens of thousands of years, he said, the dust around Fomalhaut would be “sparkling with these collisions” — like twinkling holiday lights.

Kalas first started searching for a dusty disk around Fomalhaut in 1993, hoping to see for the first time the debris left over after planet formation. Only 25 light-years from Earth, the star is young — about 440 million years old — and a proxy for what our solar system looked like in its formative years. Thanks to NASA’s Hubble Space Telescope (HST), he eventually found such a disk around the star and, in 2008, reported finding a bright spot near the disk that was likely a planet, the first to be imaged directly at visible wavelengths. He called it Fomalhaut b, per the naming convention for exoplanets.

That planet discovery has now turned to dust. What he thought was a planet was likely the dust cloud kicked up by the collision of planetesimals.

“This is a new phenomenon, a point source that appears in a planetary system and then over 10 years or more slowly disappears,” he said. “It’s masquerading as a planet because planets also look like tiny dots orbiting nearby stars.”

Based on the brightness of both the 2004 and 2023 events, the colliding objects are at least 60 kilometers (37 miles) across — at least four times larger than the object that collided with Earth 66 million years ago and killed off the dinosaurs. Objects of this size are referred to as planetesimals — objects similar in size to many of the asteroids and comets in our solar system but much smaller than a dwarf planet like Pluto.

“Fomalhaut is much younger than the solar system, but when our solar system was 440 million years old, it was littered with planetesimals crashing into each other,” Kalas said. “That’s the time period that we are seeing, when small worlds are being cratered with these violent collisions or even being destroyed and reassembled into different objects. It’s like looking back in time in a sense, to that violent period of our solar system when it was less than a billion years old.”

The 2023 Fomalhaut observations are discussed in a paper posted online Dec. 18 in the journal Science.

“The Fomalhaut 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,” said Kalas’s colleague, Mark Wyatt, a theorist and professor of astronomy at the University of Cambridge in the United Kingdom. “The exciting aspect of this observation is that it allows us to estimate both the size of the colliding bodies and how many of them there are in the disk, information which it is almost impossible to get by any other means.”

He estimates that there are about 300 million objects around Fomalhaut the size of the ones that collided to generate these bright clouds of dust. Previous observations of the star detected the presence of carbon monoxide gas, which indicates that these planetesimals are volatile-rich and therefore very similar in composition to the icy comets in our solar system, he said.

Dust clouds masquerading as exoplanets

Fomalhaut, located within the southern constellation Piscis Austrinus, is 16 times more luminous than our sun and one of the brightest stars in the sky. After Kalas began observing it with HST in 2004, he discovered a large belt of dusty debris at a distance of 133 astronomical units (AU) from the star, more than three times the distance from the star as the Kuiper Belt is from the sun in our solar system. An AU is the average distance between the Earth and the sun, or 93 million miles.

A composite Hubble Space Telescope image of the dust belt around the bright star Fomalhaut (obscured at center) showing the locations of bright spots detected in multiple images from 2004 to 2013 (cs1) and in two images in 2023 and 2024 (cs2). In the inset, dust cloud cs1, imaged in 2012, is pictured with dust cloud cs2, imaged in 2023. Astronomers now think these were caused by collisions of large objects that produced a dust cloud that reflects starlight. Image credit:
NASA, ESA, Paul Kalas/UC Berkeley

To Kalas, the belt’s sharp inner edge suggested that it had been sculpted by planets. After a second observation in 2006, he concluded that a bright spot in the outer belt visible in both the 2004 and 2006 images was, in fact, a planet. He acknowledged at the time that it could be a very bright dust cloud caused by a collision in the disk, but the likelihood of that seemed very low.

Kalas was able to schedule four follow-up HST observations of Fomalhaut, in 2010, 2012, 2013 and 2014. In the last, however, Fomalhaut b was nowhere to be seen. Nine years later, after three failed attempts to image Fomalhaut with HST, he obtained a new image that revealed another bright spot not far from the first, which is now referred to as Fomalhaut cs1, for circumstellar source 1. Based on its location, however, the new spot, dubbed Fomalhaut cs2, could not be a reappearance of Fomalhaut cs1. Because of the nine-year hiatus between the observations in 2014 and 2023, it’s unclear when Fomalhaut cs2 appeared.

In the new paper, Kalas and an international team of astronomers analyzed the 2023 image of Fomalhaut and a subsequent, though poor image obtained in 2024, and concluded that it could only be light reflected from a dust cloud produced by the collision of two planetesimals.

Kalas noted that at first, Fomalhaut cs1 moved like an exoplanet, but by 2013 its path had curved away from the star. This type of motion would be possible for very small particles being pushed outward by the radiation pressure of starlight. The appearance of cs2 supports the idea that cs1 was in fact a dust cloud.

Kalas compares these events to the dust cloud generated in 2022 when NASA’s DART (Double Asteroid Redirection Test) mission slammed into the moonlet Dimorphos, which was orbiting the asteroid Didemos. The cloud around Fomalhaut is about a billion times larger, the team estimated.

Kalas has been awarded time over the next three years to use the James Webb Space Telescope’s Near-Infrared Camera (NIRCam) and the HST to observe Fomalhaut and track the evolution of the cloud to see if it expands in size and determine its orbit. It is already 30% brighter than Fomalhaut cs1. Additional observations in August 2025 confirmed that cs2 is still visible.

In anticipation of future space missions to directly image exoplanets, Kalas cautioned astronomers to be on the lookout for dust clouds masquerading as planets.

“These collisions that produce dust clouds happen in every planetary system,” he said. “Once we start probing stars with sensitive future telescopes such as the Habitable Worlds Observatory, which aims to directly image an Earth-like exoplanet, we have to be cautious because these faint points of light orbiting a star may not be planets.”

Source: UC Berkeley

Since the previous update on 14 November 2025 and as of 12 December 2025 (data collection period), 26 818 Chikungunya virus disease (CHIKVD) cases have been detected, including 83 associated deaths, from 12 countries (data available until 30 November). Cases reported in November have decreased by 39.4% compared to October, when 44 295 were reported. Deaths have increased in November when compared to the previous month, when one death was reported.

New countries reporting cases 

Mexico has reported CHIKVD cases in November and for the first time in 2025. Ongoing CHIKVD outbreaks worldwide Currently, 14 countries have ongoing CHIKV outbreaks (time window of last 60 days). Of these, the majority are in the Americas and Asia. 

The Americas

Argentina: CHIKVD cases are reported through the year in the country. Most of the cases located in the Central, North-Eastern and Nort-Western departments of the country, while nearly no cases are reported in the Southern departments. During epidemiological weeks 31 to 48, the departments reporting the highest number of cases are Cordoba (Central), Salta (North-East), and Chaco (North-West). CHIKVD cases in Argentina have increased during the period October-November when compared to August-September 2025.

Barbados: The country continues to report sporadic cases of CHIKVD in 2025. The first cases were reported between January and March (six), while cases were later reported in September (three) and November (two), bringing the total number of CHIKVD cases in 2025 to 11. Case numbers reported in 2025 are similar to 2024. 

Bolivia: CHIKVD cases have been reported in six out of nine departments: Santa Cruz, Beni, Pando, Cochabamba, Chuquisaca, and Tarija. These departments are located in the eastern side of Bolivia, in the Andean region. Santa Cruz continues to be the most affected department, reporting most of CHIKVD cases in Bolivia, as well as all CHIKVD associated deaths. Guillain-Barre syndrome cases associated to CHIKVD have been reported in Bolivia. 

Brazil: CHIKVD cases continue to be reported in all regions (Centro-Oeste, Nordeste, Norte, Sudeste and Sul) and in most federal units of the country. The Centro-Oeste, Nordeste, and Sudeste regions account for the highest number of cases in the last four reported epidemiological weeks (45-48), where Mato Grosso Do Sul, Minas Gerais, and Sao Paulo are the most affected federal units. During the last three months (July-November), CHIKVD cases have continuously declined. Even though previous years’ trends (2023 and 2024) suggested CHIKVD cases would start increasing by November, reported CHIKVD cases in November 2025 suggest the opposite, where CHIKVD cases continue to be at similar levels as in August-September 2025. This year, most of the cases have been reported among females (60%), being the 20 to 29 years age group the most affected one. 

Colombia: CHIKVD cases are sporadically reported in Colombia. In 2025, 45 CHIKVD cases have been reported until 30 November, which is a decrease in the number of cases when compared with the same period from previous years (2022-2024). CHIKVD laboratory confirmed cases have been reported from Antioquia and Atlantico departments. 

Cuba: The current CHIKVD outbreak in Cuba continues affecting all 14 provinces of the island. The most affected provinces are Matanzas, La Habana, Camaguey, Cienfuegos, Artemia, and Villa Clara. These provinces have accounted for most of the reported cases in Cuba in previous months. During November, the first CHIKVD associated deaths have been reported this year in the country.

El Salvador: CHIKVD cases have been sporadically reported in the country during 2025. In November 2025, seven new CHIKVD cases have been reported, bringing the total to 23. So far, no CHIKVD associated deaths have been reported in 2025. This is the lowest number of CHIKVD cases reported for the same period since 2021. 

Guatemala: CHIKVD cases have been sporadically reported in the country during 2025, reaching a total of 24 cases reported by November. This is a decrease of CHIKVD cases reported in the country when compared to the same period since 2021. 

Honduras: CHIKVD cases have been sporadically reported in the country during 2025, reaching a total of 12 cases reported by November. This is an increase of CHIKVD cases reported in the country when compared to to the same period since 2023. 

Mexico: Locally acquired CHIKVD cases have been sporadically reported in the country in 2025, reaching a total of six cases. Of these, two were reported in November from Chiapas and Quintana Roo States. In 2025, CHIKVD cases have been reported from Chiapas (1), Quintana Roo (4), and Yucatan (1). No deaths have been reported in 2025. In 2024, no CHIKVD cases were reported, while in 2023 two cases were reported from Bahia California Sur and Chiapas. 

Uruguay: CHIKVD cases have been sporadically reported in the country during 2025, reaching a total of eight cases reported by November. This is an increase of CHIKVD cases reported in the country when compared with 2024. CHIKVD cases notifications have decreased in the country since the national scale outbreak of 2023, which is considered the largest outbreak ever documented in the country mainly affecting Central, Asuncion, and Alto Parana departments. 

In 2025, there have been 291 066 CHIKVD disease cases and 201 associated deaths reported in the region. This is a decrease of 29.4% compared to the same period of the previous year. The most affected subcontinental region is South America, with Brazil reporting the highest number of cases in 2025.

Asia

China: CHIKVD cases continue to be reported in Guangdong province, following the first notified case in July 2025. Most of the cases are now reported from Shenzhen, Jiangmen, and Shantou cities. Weekly number of cases reported in Guangdong province show a decreasing trend (epidemiological weeks 45-48), reaching the lowest number of cases reported since the start of the outbreak. Outside of Guangdong province, CHIKVD cases have been also reported from the Special Administrative Region of Hong Kong and Guangxi province. Initial cases have been associated with imported cases from Guangdong province. 

Pakistan: CHIKVD cases are reported throughout the year in Pakistan, concentrated in Baluchistan, Khyber Pakhtunkhwa, and Sindh provinces. These provinces are located in the Southwest of the country. Of these provinces, the highest number of CHIKVD cases is reported from Sindh, a province bordering with India. In November 2025, CHIKVD cases continued to be reported from Khyber Pakhtunkhwa, and Sindh provinces at lower levels when compared to previous four months (JulyOctober). 

Singapore: CHIKVD cases have been reported in the country since early August. Cases continued to be reported in September and October. No new CHIKVD cases were reported in November. The initial outbreak reported in August has been associated with travellers returning from Guangdong province, China. 

In 2025, there have been 136 747 CHIKVD cases and no associated deaths in the region. This is a decrease of 31.8% compared to the same period of the previous year. The most affected subcontinental region is Southeast Asia, with India reporting the highest number of cases in 2025.

Africa

In 2025, there have been 2 197 CHIKVD cases and no associated deaths in the region. This is an increase compared to the same period of the previous year. The most affected subcontinental region is East Africa, with Mauritius reporting the highest number of cases in 2025.

Europe

For CHIKVD cases reported in mainland EU/EEA, please refer to the dedicated ECDC webpage. CHIKVD cases have been reported from the French outermost regions of Réunion and Mayotte

Other countries reporting CHIKV disease cases in 2025 

Other countries have also reported CHIKVD cases in 2025; however no new cases have been notified in the last two months, these countries are: Comoros, Costa Rica, India, Kenya, Mauritius, Paraguay, Peru, Senegal, and Sri Lanka.

Global overview 

In 2025, there have been 485 908 CHIKVD cases and 229 associated deaths reported worldwide, including cases reported in the EU/EEA and outermost regions. Cases have increased when compared to the same period in 2024.