Artist\u2019s impression of the trans-Neptunian object (612533) 2002 XV93 blocking the light from a distant star<\/p>\n
NAOJ\/Ko Arimatsu<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
A small icy body as far away as Pluto has stunned scientists with the revelation that it has an atmosphere.<\/p>\n
The object, located in the Kuiper Belt of distant frozen bodies at the edge of the solar system, is formally named (612533) 2002 XV93<\/sub>, after the date of its discovery nearly a quarter of a century ago. It has a diameter of less than 500 kilometres.<\/p>\n The object also belongs to a class of objects known as plutinos because they are in the same stable orbit as Pluto, completing three revolutions around the sun for every two made by Neptune.<\/p>\n On 10 January 2024, 2002 XV93<\/sub> passed in front of a distant star, causing what is called an occultation. Ko Arimatsu at Kyoto University and his colleagues observed this event from three locations in Japan.<\/p>\n If the body had no atmosphere, the star\u2019s light would have disappeared and reappeared almost instantaneously when it went behind 2002 XV93<\/sub>.<\/p>\n But instead, the team saw the star gradually fade and recover over about 1.5 seconds near the edge of the shadow.<\/p>\n \u201cThese gradual changes are best explained if the star\u2019s light was bent by a very thin atmosphere around 2002 XV93<\/sub>,\u201d says Arimatsu.<\/p>\n The team estimates a surface pressure of about 100 to 200 nanobars, roughly 5 million to 10 million times thinner than Earth\u2019s atmosphere and about 50 to 100 times thinner than Pluto\u2019s tenuous atmosphere.<\/p>\n <\/p>\n \u201cYou could not breathe it, feel wind from it, or see anything like Earth\u2019s sky,\u201d says Arimatsu. \u201cBut it is not negligible scientifically because even such a thin atmosphere can measurably bend starlight, and it tells us that volatile gases are present or being supplied around a very small icy body.\u201d<\/p>\n The team couldn\u2019t determine the composition of the atmosphere directly from the data. Arimatsu suggests methane, nitrogen and carbon monoxide are the most plausible candidates because they are among the few substances volatile enough to become gases at the very low temperatures of the outer solar system.<\/p>\n Another mystery is what has caused the atmosphere to form, with possibilities including volcanic activity, outgassing from the interior of 2002 XV93<\/sub> or even a cosmic collision.<\/p>\n \u201cThis discovery challenges our conventional view of small worlds in the outer solar system,\u201d says Arimatsu. \u201cUntil now, clearly detectable atmospheres in the solar system were essentially associated with planets, dwarf planets and some large satellites. 2002 XV93 <\/sub>appears to be one of the smallest solar system bodies yet with a clearly detected atmosphere.\u201d<\/p>\n \u201cThere is an atmosphere, and we don\u2019t understand why,\u201d says Ben Montet at the University of New South Wales in Sydney, Australia.<\/p>\n \u201cIf you\u2019re standing on the surface of this object, you\u2019re not going to see a sky like [what] we have. But it certainly challenges the assumption that even a thin, transient atmosphere can\u2019t exist on a body this small.\u201d<\/p>\n Spend a weekend with some of the brightest minds in science, as you explore the mysteries of the universe in an exciting programme that includes an excursion to see the iconic Lovell Telescope.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<\/section>\n Topics:<\/p>\n<\/section><\/div>\n![\"Jodrell](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2025\/01\/15113200\/img_6300.jpeg\")
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