An invisible companion with giant rings hides a star

An artist’s impression of the stellar dimming event caused by a brown dwarf or super-Jupiter with massive rings (foreground) forming an opaque

doi.org/10.1093/mnras/staf2251
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#ASASSN24fw

Astronomers have discovered something very curious happening to a star called ASASSN-24fw, located in the constellation Monoceros, about 3,200 light-years from Earth

This star, which is approximately twice the size of our Sun, has always been considered quite stable and bright for decades.

But, at the end of 2024, it began to dim drastically, losing about 97% of its normal brightness.

The dimming lasted more than nine months, which is extremely rare and long for this type of phenomenon.

An international team of scientists, led by researcher Sarang Shah, carefully analyzed the case and recently published the results.

They believe that the culprit behind this “blackout” is not an ordinary planet or star, but rather an invisible object orbiting the main star: it could be a brown dwarf (a type of object located between a giant planet and a small star, incapable of nuclear fusion like stars) or a very large planet, called a “super-Jupiter.” What makes this case special are the enormous rings around this companion object.

These rings are so large and dense that they form a kind of giant disk or “dish,” about 0.17 astronomical units in diameter-to give you an idea, this is equivalent to almost half the distance between the Sun and Mercury.

When this ring-shaped disk passed in front of the star, it blocked almost all of its light for a long period, causing the gradual and prolonged dimming that telescopes recorded.

This type of event is extremely rare because it requires a perfect alignment between the star, the rings, and our line of sight here on Earth.

Scientists used brightness (photometric) measurements and light (spectroscopic) analyses, as well as computational models, to reach this conclusion.

They also noted evidence that there may be remnant material from ancient collisions between planets or fragments of disks around the star, which is unusual for such an old star (probably over a billion years old).

Researchers predict that something similar could happen again in about 42 or 43 years, when the rings realign in the same way.

Future observations with powerful telescopes, such as the Very Large Telescope and the James Webb, should help to better understand the composition, temperature, and exact age of this intriguing system.

This discovery shows how distant star systems can have complex and unexpected structures, such as giant rings in objects we don’t see directly, and helps scientists learn more about how planets and disks form and evolve in the universe.

Published in 02/12/2026 08h10

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Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.

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