Scientists are puzzling over another oddball on the edge of the solar system: This time, it’s an icy object less than a quarter of Pluto’s size with a thin atmosphere – a layer of gas that’s not typically found around objects so small.
A Japanese team of researchers — including an amateur astronomer — laid out the curious case of 2002 XV93 this week in the journal Nature Astronomy. 2002 XV93 traces an elliptical path beyond the orbit of Neptune in the icy Kuiper Belt, never coming closer to the sun than 3 billion miles. Like Pluto, it’s locked in a resonance with Neptune that keeps its orbit relatively stable.
The Japanese astronomers, led by Ko Arimatsu of the National Astronomical Observatory of Japan, tracked the mini-world with several telescopes as it passed in front of a background star in January 2024. They found that the light from the star gradually dimmed before it disappeared behind 2002 XV93, as if the light was filtered through a thin layer of gas.
That finding posed a puzzle: Based on estimates of its size, 2002 XV93 shouldn’t have enough gravitational pull to hold onto an atmosphere for longer than, say, 1,000 years.
Follow-up observations from NASA’s James Webb Space Telescope produced no evidence that there were frozen gases on the object’s surface. That led Arimatsu and his colleagues to suggest that gases are being spewed out from ice volcanoes, or that a cometary impact released a burst of gas that will eventually dissipate.
The spectral signature of the filtered light would be consistent with an atmosphere containing nitrogen, methane or carbon monoxide — chemicals that are found in Pluto’s somewhat less thin atmosphere. Further observations will be required to verify the atmosphere’s composition.
“This is an amazing development, but it sorely needs independent verification. The implications are profound if verified,” Alan Stern, a planetary scientist at Southwest Research Institute who leads NASA’s New Horizons mission to Pluto and the Kuiper Belt, told The Associated Press.
If 2002 XV93 can hold onto a stable atmosphere, perhaps fed by the emissions of ice volcanoes, other underappreciated celestial bodies might be able to do so as well. “This discovery suggests that the traditional idea that global dense atmospheres form only around larger planets must be revised,” the researchers write.
This week’s findings have come amid hints that Pluto — an oddball world that was reclassified as a dwarf planet in 2006 — may get a second look. “I am very much in the camp of ‘make Pluto a planet again,’ ” NASA Administrator Jared Isaacman said during a Senate committee hearing last month. “And I would say we are doing some papers right now on, I think, a position that we would love to escalate through the scientific community to revisit this discussion.”
The senator who asked Isaacman about Pluto was Kansas Republican Jerry Moran — who represents the state where Clyde Tombaugh, Pluto’s discoverer, grew up. The NASA chief alluded to that fact when he said he wanted to “ensure that Clyde Tombaugh gets the credit he received once and rightfully deserves to receive again.” So, Isaacman may have said what he said merely as a political gesture.
As the author of “The Case for Pluto,” I’m fine with Pluto’s present status as one of the solar system’s first five officially recognized dwarf planets. But if someone wants to Make Pluto Great Again, who am I to complain?
In addition to Arimatsu, the authors of the paper published by Nature Astronomy, “Detection of an Atmosphere on a Trans-Neptunian Object Beyond Pluto,” include Fumi Yoshida, Tsutomu Hayamizu, Satoshi Takita, Katsumasa Hosoi, Takafum Ootsubo and Jun-ichi Watanabe. Hayamizu is the amateur astronomer in the group.
This report was published on Universe Today with the headline “Pluto-Like World’s Thin Atmosphere Poses a Mystery for Astronomers.” Licensed for republication under Creative Commons Attribution 4.0 International License.
