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- Astronomers watched a giant gas cloud pass in front of its star and dim it for nearly nine months. During this rare event, they acquired spectra of the gas cloud; that is, they broke the light from the cloud into a range of wavelengths, in order to analyze it.
- The data indicate this cloud is gravitationally bound to a secondary object that itself orbits the star in the outer reaches of its planetary system
- What is the hidden object? Astronomers say it could be a planet, brown dwarf or small star. It likely formed when two objects collided in the outer reaches of this distant solar system.
NOIRLab published this original story on January 21, 2026. Edits by EarthSky.
Astronomers detect mysterious object in giant gas cloud
In September 2024, a star 3,000 light-years away suddenly became 40 times dimmer than usual. And it remained dim until May 2025. The star, J0705+0612, is similar to our sun. So its stark dip in brightness caught the attention of Nadia Zakamska, professor of astrophysics at Johns Hopkins University. Zakamska said:
Stars like the sun don’t just stop shining for no reason, so dramatic dimming events like this are very rare.
Recognizing the opportunity to study such an event over many months, Zakamska and her team initiated observations with the Gemini South telescope located on Cerro Pachón in Chile, as well as the Apache Point Observatory 3.5-meter telescope and the 6.5 meter Magellan Telescopes.
The researchers published their findings in a peer-reviewed paper in The Astronomical Journal on January 21, 2026.
A cloud of gas and dust and a mystery object
They combined their observations with archival data on J0705+0612. What they found was that a vast, slow-moving cloud of gas and dust had temporarily passed in front of the star. They estimate the cloud is about 1.2 billion miles (2 billion km) from its host star and roughly 120 million miles (200 million km) in diameter.
The data indicate this cloud is gravitationally bound to a secondary object that itself orbits the star in the outer reaches of its planetary system. While the nature of this object remains unknown, it must be massive enough to hold the cloud together. Observations constrain it to be at least a few times the mass of Jupiter, though it could be larger. Possibilities range from a planet to a brown dwarf to an extremely low-mass star.
If the mystery object is a star, the cloud would be classified as a circumsecondary disk, or a debris disk orbiting the less massive member of a binary system. If the object is a planet, it would be a circumplanetary disk. In either case, directly observing a star as it is occulted by a disk surrounding a secondary object is exceptionally rare, with only a handful of known examples.
A close look at the cloud’s composition
To investigate the cloud’s composition, the team used the Gemini High-resolution Optical SpecTrograph (GHOST). In March 2025, GHOST observed the occultation for just over two hours. It dispersed the light from the star into a spectrum that reveals the chemical elements present in the intervening material. Zakamska said:
When I started observing the occultation with spectroscopy, I was hoping to unveil something about the chemical composition of the cloud, as no such measurements had been done before. But the result exceeded all my expectations.
The GHOST data revealed multiple metals – elements heavier than helium – within the cloud. More remarkably, the high precision of the spectra allowed the team to directly measure how the gas is moving in three dimensions. This marks the first time astronomers have measured the internal gas motions of a disk orbiting a secondary object such as a planet or low-mass star. The observations show a dynamic environment with winds of gaseous metals, including iron and calcium. Zakamska said:
The sensitivity of GHOST allowed us to not only detect the gas in this cloud, but to actually measure how it is moving. That’s something we’ve never been able to do before in a system like this.
Chris Davis, NSF Program Director for NOIRLab, added:
This study illustrates the considerable power of Gemini’s newest facility instrument, GHOST, and further highlights one of Gemini’s great strengths: rapidly responding to transient events like this occultation.
How did the mysterious object and giant gas cloud form?
The precise measurements of the speed and direction of the wind show that the cloud is moving separately from its host star. This, combined with how long the occultation lasted, further confirm that the occulter is a disk around a secondary object and that it orbits in the outer reaches of its host star’s stellar system.
The source shows infrared excess, typically associated with disks around young stars. However, J0705+0612 is more than 2 billion years old, meaning the disk is unlikely to be leftover debris from the system’s early planet formation stage. So how did it form?
Zakamska proposes that it originated after two planets collided with each other in the outer reaches of this star’s planetary system, ejecting dust, rocks and debris and forming the massive cloud now seen passing in front of the star.
The discovery highlights how new technology enables new insights into the universe. GHOST has opened a new window into studying hidden phenomena in distant star systems. And the findings provide valuable clues about the long-term evolution of planetary systems and how disks can form around old stars. Zakamska said:
This event shows us that even in mature planetary systems, dramatic, large-scale collisions can still occur. It’s a vivid reminder that the universe is far from static: it’s an ongoing story of creation, destruction and transformation.
Bottom line: Astronomers witnessed a giant gas cloud pass in front of its star. And they said a mysterious object is within the gas cloud: likely a planet, brown dwarf or small star.
Source: ASASSN-24fw: Candidate Gas-rich Circumsecondary Disk Occultation of a Main-sequence Star
Via NOIRLab