"The Associated Press is reporting on a new study in Nature Astronomy suggesting that a tiny, icy world beyond Pluto harbors a thin, delicate atmosphere that may have been created by volcanic eruptions or a comet strike," writes longtime Slashdot reader fahrbot-bot. From the report: Just 300 miles (500 kilometers) or so across, this mini Pluto is thought to be the solar system's smallest object yet with a clearly detected global atmosphere bound by gravity, said lead researcher Ko Arimatsu of the National Astronomical Observatory of Japan. This so-called minor planet -- formally known as (612533) 2002 XV93 -- is considered a plutino, circling the sun twice in the time it takes Neptune to complete three solar orbits. At the time of the study, it was more than 3.4 billion miles (5.5 billion kilometers) away, farther than even Pluto, the only other object in the Kuiper Belt with an observed atmosphere. This cosmic iceball's atmosphere is believed to be 5 million to 10 million times thinner than Earth's protective atmosphere, according to the the study [...].

It's 50 to 100 times thinner than even Pluto's tenuous atmosphere. The likeliest atmospheric chemicals are methane, nitrogen or carbon monoxide, any of which could reproduce the observed dimming as the object passed before the star, according to Arimatsu. Further observations, especially by NASA's Webb Space Telescope, could verify the makeup of the atmosphere, according to Arimatsu.

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