Star dims for 9 months, likely due to giant ringed object
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- A star called ASASSN-24fw dimmed by 97% for more than nine months. It was one of the longest stellar dimming events ever recorded. But why did it get so dim for so long?
- Astronomers think an unseen brown dwarf or super-Jupiter with a huge ring system passed in front of the star, blocking its light.
- The researchers expect the star to dim again in about 42 or 43 years. At that time, astronomers can carry out further analysis to find out more about this fascinating system.
Star dims for 9 months, likely due to giant ringed planet
One of the longest stellar dimming events ever observed was likely caused by the gigantic saucer-like rings of either an unseen “super-Jupiter” or a brown dwarf blocking its host star’s light. That’s according to astronomers at the Royal Astronomical Society, who described the new research on the fading star on February 12. 2026. The star, named ASASSN-24fw, sits 3,200 light-years from Earth and is about twice as big as our sun. For decades, astronomers had observed the star as stable, but at the end of 2024 it faded dramatically.
It then remained this way for more than nine months, far longer than is normal for an event like this. The unusual length of the dimming sparked confusion among researchers and prompted speculation as to what could have caused such an “extremely rare” phenomenon.
Now, in a new study published February 12, 2026, in the peer-reviewed Monthly Notices of the Royal Astronomical Society, a team of international researchers propose a solution of the riddle of this mysterious star in the Monoceros constellation.
They think it was most likely a brown dwarf (an object between the size of a star and Jupiter) with Saturn-like rings that caused ASASSN-24fw to dim by about 97%. This ring system is so enormous it extends out about 0.17 astronomical units (AU), comparable to half the distance between our sun and Mercury.
Brown dwarf or super-Jupiter
The two most likely objects responsible for blocking the star’s light are a brown dwarf or super-Jupiter.
Brown dwarfs are mysterious objects. They’re too big to be a planet but also too small to be a star. They lack the mass to keep fusing atoms and blossom into fully fledged suns.
The other option, the researchers said, is a super-Jupiter. These are massive gas giant exoplanets that exceed the mass of Jupiter and bridge the gap between brown dwarfs and planets.
Their findings offer a glimpse into complex planetary-scale structures beyond our solar system. And they pave a new way to study how planets and their rings may form and evolve around other stars.
Unlike typical eclipses, which usually last days or weeks, this dimming continued for nearly 200 days, making it one of the longest ever observed.
Lead author Sarang Shah, a post-doctoral researcher at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), in Pune, India, said:
Various models made by our group show that the most likely explanation for the dimming is a brown dwarf – an object heavier than a planet but lighter than a star – surrounded by a vast and dense ring system. It is orbiting the star at a farther distance with the ring.
Long-lasting dimming events like this are exceptionally uncommon as they require very perfect lineups. The dimming began gradually because the outer parts of the rings are thin, and only became obvious when the denser regions passed in front of the star.
Large ring system
Analysis of photometric and spectroscopic studies of the event suggests that the companion object has a mass of more than three times that of Jupiter.
The analysis also shows that ASASSN-24fw itself has a circumstellar environment (possibly remnants from past or ongoing planetary collisions) very near to it, which is unusual for a star of this age (likely more than 1 billion years).
Co-author Jonathan Marshall, an independent post-doctoral researcher affiliated with Academia Sinica, Taiwan, has expertise is in circumstellar material and debris discs. Marshall said:
Large ring systems are expected around massive objects, but they are very difficult to observe directly to determine their characteristics. This rare event allows us to study such a complex system in remarkable detail. In fact, while studying this dimming, we also serendipitously discovered that ASASSN-24fw also has a red dwarf star in its vicinity.
The team of researchers now want to measure the temperature, evolutionary status, chemical composition and age of the star that dimmed. They then hope to obtain more data from the European Southern Observatory’s Very Large Telescope in Chile and the James Webb Space Telescope to better understand the evolution of such systems and relate them to planetary formation theories.
The researchers expect the star to dim again in about 42 or 43 years’ time. At that time, astronomers can carry out further analysis to find out more about this fascinating system.
Bottom line: Astronomers watched a star dim to less than 97% of its brightness for nine months. They believe a giant ringed object blocked the light from our view.
Via Royal Astronomical Society
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