Astronomers hoping to observe planets around nearby stars have witnessed an “unprecedented astronomical phenomenon” that is much rarer, the researchers said. It is the violent aftermath of not one, but two collisions between the planet’s rocky components.
Over the past two decades, astronomers have witnessed two catastrophic collisions around the star Fomalhaut, located just 25 light-years away in the constellation Austrinus Pisces. The detection occurred after planetesimals (rocky fragments of unformed planets), much larger than the asteroid that wiped out the dinosaurs, collided with each other, creating giant clouds of shimmering debris.
Fomalhaut systems are not immune to such crashes. It is famously known as the “Eye of Sauron” because of its resemblance to the all-seeing fiery eye from JRR Tolkien’s The Lord of the Rings series. This similarity stems from the spectacular dust belt that surrounds Fomalhaut at a distance of 133 astronomical units (AU), where 1 AU is equivalent to the average distance between the Sun and Earth, 93 million miles (150 million km).
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This belt of dust and debris, formed by countless rock and ice collisions, provides a dustier analog of the early solar system that emerged more than 4 billion years ago, offering a glimpse into the chaotic infancy of our neighborhood, when planets were being created, destroyed and rebuilt, the researchers said.
false planet syndrome
A new study conducted by an international research team led by astronomer Paul Karas of the University of California, Berkeley, describes these two collision events in devastating detail to help solve planetary mysteries.
In the early 2000s, astronomers observing the Fomalhaut system discovered a large, shiny object that many thought was an exoplanet covered in reflective dust. They designated this exoplanet candidate Fomalhaut b.
But over the course of about 20 years, when the supposed planet blinked out and another bright spot of light appeared nearby, researchers realized that they were not looking at a planet at all, but a cloud of glowing debris formed by what they called a “cosmic fender bender.”
Fomalhaut Forensics: A History of the Catastrophic Crash
The two collision events, now known as Fomalhaut CS1 and Fomalhaut CS2, appear to have happened incredibly coincidentally. According to theory, an impact of this magnitude should occur only once every 100,000 years, but the Fomalhaut system surprised scientists by having two such impacts in just 20 years.
In fact, based on this timeline, the study estimates that 22 million similar events may have occurred so far during the Fomalhaut system’s relatively young 440 million-year lifespan. Even if we could only rewind the past 3,000 years or so, “Fomalhaut’s planetary system would be glowing with these collisions,” Karas explained in a statement.
Reverse engineering of the impacts based on factors such as the mass of the debris cloud and the size of the dust particles suggests that Fomalhaut CS1 and CS2 were the result of a microplanet impact approximately 37 miles (60 km) in diameter, or about four to six times the size of the asteroid that wiped out non-avian dinosaurs 66 million years ago.
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This is an alien event with a relatable twist. “These large objects are similar to our own asteroids and the large objects that make up the Kuiper belt,” study co-author Jason Wang, an astronomer at Northwestern University, told Live Science in an email.
And there are a lot of such corpses. Based on their reconstruction of this event, the researchers suggest that the Fomalhaut system could contain 1.8 Earth masses of these protoplanetesimals. Another statement said the number could be around 300 million.
Additionally, the system holds the mass of an additional 1.8 Earths in a small object less than 0.186 miles (0.3 kilometers) in diameter. These relative runts swirl within Fomalhaut’s dust belt, constantly replenishing it with tiny, shimmering dust grains (often on the order of tens of thousands of an inch). Without this rocky reservoir, the dust belt would disappear as its particles were blown out of the system by stellar winds or swallowed by stars.
Planets that never existed may still exist
Although Fomalhaut b no longer exists, at least not as a planet, this “planet that never existed” may actually still be hiding in the system.
The researchers calculated that given certain conditions, there is about a 10% chance that Fomalhaut cs1 and cs2 are not random collisions. Their similar timing and location could indicate hidden influences, such as the ghostly gravity of invisible exoplanets.
“For example, something like a planet must be responsible for carving out the planetesimals to form the dust belts we see,” Wang told Live Science. “Furthermore, we speculate that the close location of the impact sites of cs1 and cs2 may be driven by planets preferentially causing planetesimal impacts.”
play peek-a-boo with the planets
This exoplanet mess highlights important considerations for planet hunters and next-generation facilities like NASA’s Habitable World Observatory, designed to directly image habitable zone exoplanets in nearby space. “Fomalhaut CS2 is exactly like an exoplanet that reflects starlight,” Karas explained.
As a result, this unique study not only informs our ideas about planet formation, including impact rates and debris belt dynamics, but also helps astronomers better identify planetary bodies among all the other bright objects the universe continually fascinates us with.
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