{"id":802105,"date":"2026-05-08T07:43:28","date_gmt":"2026-05-08T12:43:28","guid":{"rendered":"https:\/\/spaceweekly.com\/?p=802105"},"modified":"2026-05-08T07:43:28","modified_gmt":"2026-05-08T12:43:28","slug":"surprise-tiny-world-with-an-atmosphere-in-outer-solar-system","status":"publish","type":"post","link":"https:\/\/spaceweekly.com\/?p=802105","title":{"rendered":"Surprise! Tiny world with an atmosphere in outer solar system"},"content":{"rendered":"


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Artist\u2019s illustration of a small world passing front of a background star. When astronomers in Japan recently observed the small outer solar system object 2002 XV93, the light from the star gradually faded, indicating that this is a tiny world with an atmosphere. That\u2019s a big surprise, because this object seemed too small for an atmosphere. Image via NAOJ.<\/figcaption><\/figure>\n
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  • Most objects in our solar system are too small to sustain atmospheres,<\/strong> scientists have long thought.<\/li>\n
  • But now, astronomers have spotted a tiny world with an atmosphere<\/strong> beyond the orbit of Neptune. It should be too small for an atmosphere to be possible.<\/li>\n
  • Researchers in Japan discovered this<\/strong> by watching the object, 2002 XV93, pass in front of a distant star.<\/li>\n<\/ul>\n

    Science news, night sky events and beautiful photos,<\/strong> all in one place. Click here to subscribe to our free daily newsletter.<\/p>\n

    This tiny world has an atmosphere \u2026 but shouldn\u2019t<\/h3>\n

    Every planet in our solar system apart from Mercury has an atmosphere. The dwarf planet Pluto also has one, as does Saturn\u2019s moon Titan. But most of the objects in our solar system don\u2019t. That\u2019s because smaller bodies don\u2019t have enough mass to hold onto any kind of atmosphere \u2026 Or so we thought.<\/p>\n

    Astronomers in Japan have just discovered that the tiny world 2002 XV93, orbiting in the icy reaches beyond Neptune, does<\/em> have a thin atmosphere. That\u2019s despite the fact that this space rock is just some 310 miles (500 km) in diameter. That\u2019s about 7 times smaller than our moon.<\/p>\n

    The researchers said on May 5, 2026, that they detected the atmosphere when the tiny world passed in front of a star. Using multiple telescopes, they saw that the light from the star gradually faded instead of just suddenly winking. That\u2019s evidence for a thin atmosphere around 2002 XV93.<\/p>\n

    The researchers published their peer-reviewed findings in Nature Astronomy<\/em> on May 4, 2026. A preprint version, with no paywall, is also available on arXiv.<\/p>\n

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    Observations of a distant object beyond Pluto suggest that it is surrounded by a thin atmosphere, potentially fuelled by ice volcanoes or produced by the impact of a comet-like body, according to research in Nature Astronomy. go.nature.com\/4n5Kgup ??<\/p>\n

    \u2014 Nature Portfolio (@natureportfolio.nature.com) 2026-05-05T13:15:00.888Z<\/p>\n<\/blockquote>\n

    Spotting an atmosphere by starlight<\/h3>\n

    This tiny world is what\u2019s known as a trans-Neptunian object (TNO). That\u2019s an object that orbits the sun beyond the orbit of Neptune. Most of these bodies are much too small, with too little gravity, to hold on to any kind of atmosphere. Pluto, also classified as a trans-Neptunian object, is an exception.<\/p>\n

    When researchers noticed that 2002 XV93 was going to transit \u2013 pass in front of \u2013 a distant star, they decided to make the most of it. They used the transit as a chance to see if, unexpectedly, 2002 XV93 happened to have any trace of an atmosphere. 2002 XV93 passed in front of the star on January 10, 2024.<\/p>\n

    And, surprise: It did! The light from the star gradually dimmed as 2002 XV93 passed in front of it. If it didn\u2019t have an atmosphere, the light would have blinked out much more suddenly. So this indicated that 2002 XV93 does, in fact, have a thin atmosphere. <\/p>\n

    Lead author Ko Arimatsu at the National Astronomical Observatory of Japan mentioned in Live Science<\/em>:<\/p>\n

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    The observation data showed a smooth change of the star\u2019s brightness near the edge of the shadow, lasting about 1.5 seconds. This kind of smooth brightness change is naturally explained if the starlight was bent by a very thin atmosphere around the object.<\/p>\n<\/blockquote>\n

    But an object like 2002 XV93 should be too small to have an atmosphere. So what\u2019s going on here? Scientists don\u2019t know for sure yet.<\/p>\n