Astronomers believe they’ve detected an atmosphere around a tiny, icy world beyond Pluto
CAPE CANAVERAL, Fla. (AP) — A new study suggests that a small, icy world beyond Pluto harbors a thin, delicate atmosphere that could have been created by volcanic eruptions or a comet strike.
At just about 500 kilometers in diameter, this mini Pluto is believed to be the smallest object in the solar system to date, with a clearly detected overall atmosphere bound by gravity, said lead researcher Ko Arimatsu of the National Astronomical Observatory of Japan.
“This is an astonishing development, but it badly needs independent verification. The implications are profound if verified,” said Alan Stern of the Southwest Research Institute, the lead scientist behind NASA’s New Horizons mission to Pluto and beyond. He did not participate in the study.
This discovery offers new insight into the most distant and coldest objects in our solar system in a region known as the Kuiper Belt. Researchers used three telescopes in Japan to observe the object in 2024 as it passed in front of a background star, briefly dimming the star’s light.
“This changes our view of small worlds in the solar system, not just beyond Neptune,” Arimatsu said in an email. Finding an atmosphere around such a small object was “really surprising,” he added, and challenges “the conventional view that atmospheres are limited to large planets, dwarf planets and some large moons.”
This so-called minor planet – officially 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 5.5 billion kilometers away, farther than Pluto, the only other Kuiper Belt object with an observed atmosphere.
The atmosphere of this cosmic ice ball would be 5 to 10 million times thinner than the Earth’s protective atmosphere, according to a study published Monday in the journal Nature Astronomy.
It is 50 to 100 times thinner than Pluto’s thin atmosphere. The most likely atmospheric chemicals are methane, nitrogen or carbon monoxide, which could replicate the dimming seen as the object passed in front of the star, according to Arimatsu.
Other observations, including those by NASA’s Webb Space Telescope, could verify the composition of the atmosphere, according to Arimatsu.
“This is why future monitoring is so important,” he said. “If the atmosphere fades over the next few years, that would confirm the origin of the impact. If it persists or varies seasonally, that would be more indicative of an internal supply of gas” from ice volcanoes.
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