Astronomers often watch stars fade away as they reach the end of their lives, but one star in our galaxy gave scientists an unusual surprise when it almost completely disappeared for months, only to reappear again.
The star, called ASASSN-24fw, dimmed by about 97% between late 2024 and early 2025. For eight months, it seemed as if the star had nearly vanished before slowly returning to its normal brightness.
Such dramatic dimming events are extremely rare, and scientists rushed to figure out what could have caused it.
Now, researchers led by The Ohio State University think they may have the answer.
In a new study published in The Open Journal of Astrophysics, they argue that a large cloud of dust and gas, rather than the star itself changing, blocked the light from reaching Earth.
The key clue came from the star’s color. Normally, if a star is cooling down or heating up, its color changes.
But ASASSN-24fw’s light stayed the same shade throughout the event, suggesting the star itself wasn’t evolving. Instead, something came between us and the star—most likely a massive dusty disk.
The star itself is classified as an F-type star, slightly larger and heavier than our sun, about twice its size, and located 3,000 light-years away.
Researchers estimate that the disk of dust surrounding it is about 1.3 astronomical units across—larger than the distance between Earth and the sun.
They believe this disk is made of clusters of carbon or water ice, each similar in size to a large grain of dust on Earth. Such disks resemble the planet-forming material found around young stars, meaning ASASSN-24fw could help scientists learn more about how stars and planetary systems evolve.
But there’s more to the story. The researchers suggest that ASASSN-24fw may not be alone. They think a smaller, fainter companion star orbits it, making the system a hidden binary. This second star could be influencing the dusty disk, changing its shape and position, and causing the eclipses we see from Earth.
Events like this are not just unusual—they’re almost one-of-a-kind. Chris Kochanek, a co-author of the study, explained that when they searched for other stars with similar dimming patterns, they couldn’t find any exact matches.
This makes ASASSN-24fw even more valuable to study, as it could reveal new insights into how dust disks behave in binary systems.
The star was first detected as part of the All-Sky Automated Survey for Supernovae (ASAS-SN), a project that uses a network of small telescopes to monitor the entire night sky. Over the last decade, ASAS-SN has taken about 14 million images, capturing events big and small across the universe.
Based on their calculations, the researchers believe ASASSN-24fw goes through such eclipses roughly once every 43.8 years.
That means the next dramatic dimming likely won’t happen until around 2068. While some of today’s scientists may not be around to witness it, they hope the records they’re keeping will be available for future generations.
For now, astronomers are planning to use larger, more advanced telescopes like the James Webb Space Telescope and the Large Binocular Telescope Observatory to study the star in greater detail as it continues to shine again.
Each strange discovery like this challenges astronomers to rethink their theories, showing once again that the universe still has plenty of mysteries waiting to be solved.
Source: Ohio State University.
