Photo: NAOJ
A new study reveals that a small, icy world far beyond Pluto may have its own thin atmosphere, a discovery that could reshape scientists’ understanding of the outer solar system. Researchers led by Ko Arimatsu at the National Astronomical Observatory of Japan detected what appears to be a delicate atmosphere around the minor planet (612533) 2002 XV93, sometimes called a “mini Pluto.”
Measuring only about 300 miles across, this object is now considered the smallest known body in the solar system with a clearly detected global atmosphere held by gravity. The study suggests the atmosphere may have formed from volcanic activity or a comet strike.
Researchers used three telescopes in Japan to observe the distant world in 2024 as it briefly passed in front of a background star, causing a dimming of the starlight. This method allowed scientists to detect the atmosphere, which is believed to be five million to 10 million times thinner than Earth’s and 50 to 100 times thinner than Pluto’s.
The most likely gases making up the atmosphere are methane, nitrogen, or carbon monoxide. The object, known as a plutino, orbits the sun twice for every three orbits completed by Neptune. It was more than 3.4 billion miles from Earth when observed, farther than Pluto—the only other object in the Kuiper Belt known to have an atmosphere.
Further observations, particularly by NASA’s Webb Space Telescope, could confirm the chemical makeup of the atmosphere and reveal how long it lasts. If the atmosphere disappears in the next few years, it could support the idea of a recent impact origin. If it persists or changes seasonally, it might suggest ongoing volcanic activity.