A mysterious celestial object is the key to holding together a vast cloud of vaporized metal, spanning an astonishing 120 million miles in width.
Recently, astronomers discovered an enormous cloud that has been obscuring light from a distant star, revealing itself to be composed of swirling winds filled with vaporized metal. Even more intriguingly, this cloud seems to be gravitationally tethered to an enigmatic body, which may either be a massive planet or a low-mass star.
The tale began in September 2024, when astronomers first observed a significant dimming in a sun-like star named J0705+0612, located approximately 3,000 light-years from Earth. This star became 40 times dimmer than its usual brightness for a duration of nine months, only to return to its normal luminosity in May 2025. Such dramatic dimming events are exceptionally rare, which piqued the interest of Johns Hopkins astronomer Nadia Zakamska. "Stars similar to our sun don’t just suddenly stop shining; therefore, occurrences like this are quite unusual," she commented.
In response to this peculiar phenomenon, Zakamska and her research team utilized several telescopes, including the Gemini South telescope in Chile and the Apache Point Observatory 3.5-meter telescope, to gather more data on J0705+0612. By combining recent observations with historical data, they concluded that the star was intermittently obscured by a massive, slowly moving cloud of gas and dust.
They estimated this cloud to be about 120 million miles (200 million kilometers) wide, which is roughly 15,000 times larger than the diameter of Earth. At the time of the dimming, it was situated around 1.2 billion miles (2 billion km) away from J0705+0612, approximately 13 times the distance from Earth to the sun.
What happens next raises a compelling question: Is this bound object a low-mass star or a high-mass planet? The researchers determined that the cloud is gravitationally linked to another celestial body orbiting J0705+0612, which must possess enough mass to exert a significant gravitational pull on the cloud—suggesting it has a mass several times greater than that of Jupiter, perhaps even more.
If this object is indeed a star, then the cloud represents what is known as a circumsecondary disk—a collection of gas and dust revolving around a less massive star in a binary system. Conversely, if it's a planet, the cloud would be classified as a circumplanetary disk. Observing such a cloud blocking a star’s light is a remarkable occurrence in astronomy.
To further explore the composition of this cloud, the researchers employed the Gemini High-resolution Optical SpecTrograph (GHOST) on the Gemini South telescope. They spent two hours observing the cloud as it passed in front of J0705+0612. "My hope was to uncover details about the chemical makeup of the cloud, as no such analyses had been performed previously," said Zakamska. "The results surpassed all my expectations."
The analysis revealed that the cloud contains a wealth of elements heavier than hydrogen and helium, often referred to by astronomers as "metals." Notably, gaseous winds rich in iron and calcium were mapped in three dimensions for the first time, allowing astronomers to gauge the internal gas movements within a disk orbiting a secondary body like a planet or low-mass star.
Zakamska emphasized the capabilities of GHOST, stating, "This instrument enabled us not only to detect the gas present in this cloud but also to measure its motion, something we had never achieved in a similar system before."
By understanding the speed and direction of the winds in the cloud, the research team confirmed that it moves independently from its host star, reinforcing the notion that it is linked to a secondary entity residing in the outer reaches of this planetary system.
The researchers speculate that the cloud may have formed from a collision between two planets orbiting J0705+0612, resulting in debris being ejected into space. While such events are relatively common in younger, chaotic planetary systems, they are unexpected in a system believed to be around 2 billion years old.
"This discovery serves as a reminder that even mature planetary systems can still experience catastrophic collisions," Zakamska remarked. "It highlights the dynamic nature of the universe — a continuous saga of creation, destruction, and transformation."
The findings of this intriguing research were published on January 21 in The Astronomical Journal.
