doi.org/10.1038/s41550-026-02846-1
Credibility: 989
#Solar System
Scientists have discovered something surprising in the outer reaches of the Solar System
Far beyond Neptune’s orbit lies a small, icy world, about 500 kilometers in diameter, possessing a thin, tenuous atmosphere.
The most intriguing aspect is that, according to what was previously known, an object so small and with such weak gravity should not be able to retain any atmosphere.
However, it is there, challenging our ideas about how celestial bodies retain gases around them.
This object, called (612533) 2002 XV93, is a plutino – a type of icy body that orbits the Sun in resonance with Neptune, at a distance about 40 times that of Earth.
These distant worlds, located in the Kuiper Belt, are like fossils from the early Solar System.
They hold valuable information about the formation of planets and the movement of materials when the system was still young.
But studying them is extremely difficult: they are very small, dark, and distant, reflecting little light to our telescopes.
The detection of the atmosphere was only possible thanks to a rare event called a stellar occultation.
In 2024, Japanese astronomers, led by Ko Arimatsu of the National Astronomical Observatory of Japan, were fortunate enough to observe the exact moment when 2002 XV93 passed in front of a distant star.
Using three different observation locations in Japan, they precisely recorded how the star’s light was blocked by the object.
In a body without an atmosphere, the star’s light would disappear abruptly and reappear in the same way.
But the data showed something different: for about 1.5 seconds before and after the total blockage, which lasted between 15 and 20 seconds, the light gradually decreased and increased.
This can only be explained if the light passed through a layer of gas that refracted (bent) it slightly.
Models based on Pluto’s atmosphere have indicated that it is extremely rarefied, composed mainly of methane, nitrogen, or carbon monoxide, with a pressure of only 100 to 200 nanobars – about 5 to 10 million times thinner than Earth’s atmosphere at sea level.
This discovery is impressive for two main reasons.
First, it demonstrates that our current instruments and techniques are capable of detecting almost non-existent atmospheres on very distant objects.
Second, calculations show that such a fragile atmosphere should dissipate in just a few hundred or thousand years due to low gravity.
For it to still exist today, it needs to be replenished somehow.
The researchers propose two main explanations.
One is that a comet recently collided with the object, releasing gases that formed this temporary atmosphere.
Another possibility is the existence of active cryovolcanoes – ice volcanoes that would expel icy mud and gases from the interior of the body, constantly renewing the atmosphere that escapes into space, as possibly happens on Pluto.
This is the first time an atmosphere has been confirmed on a small trans-Neptunian object other than Pluto.
The finding suggests that even tiny worlds can have atmospheres, at least for short periods, and that we need to revise the idea that only large planets can retain gases around them.
As the authors wrote in the article published in the journal Nature Astronomy: “Even an object a few hundred kilometers across in the Kuiper Belt can harbor, at least temporarily, an atmosphere.
Our results indicate that a fraction of these distant icy bodies may have atmospheres sustained by cryovolcanic activity or recent impacts.”
This observation not only expands our knowledge of the outer reaches of the Solar System, but also opens new possibilities for studying other distant objects with innovative techniques.
What seemed impossible may be more common than we imagined, revealing that the Universe continues to be full of surprises in the coldest and darkest places.
Published in 05/05/2026 20h13
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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