In the cold, distant reaches of our solar system lies a small object called (612533) 2002 XV93. Surprisingly, it has developed an atmosphere, leaving scientists puzzled about how and why this occurred.
One theory suggests it could be from cryovolcanism—essentially ice volcanoes that release gas. Another possibility is that a recent impact event deposited gases. However, any atmosphere this thin would normally escape into space within about a thousand years.
This small object, only about 310 miles wide, is classified as a trans-Neptunian object (TNO) and is a “plutino,” orbiting the sun in a pattern similar to Pluto. Unlike Pluto, which maintains a stable atmosphere closer to the sun, (612533) 2002 XV93 is much smaller and colder, making its newfound atmosphere all the more curious.
The atmosphere’s pressure is incredibly thin—100 to 200 nanobars, which is five to ten million times less dense than Earth’s atmosphere. This contrasts sharply with Pluto’s atmosphere, which is about 10 millibars. The lack of common atmospherics like nitrogen or methane on (612533) 2002 XV93 baffles astronomers. Historical data from the James Webb Space Telescope found no ice sources that could turn into gas on its surface, making the current presence of an atmosphere even more perplexing.
Researchers, including Ko Arimatsu from the Ishigakijima Astronomical Observatory, observed the object passing in front of a star, known as stellar occultation, on January 10, 2024. This event was key in discovering its atmosphere. If (612533) 2002 XV93 were truly airless, the star would abruptly disappear as it passed behind it. But that’s not what happened; the team noted a gradual fade, indicating an atmosphere was present.
This revelation could shake up our understanding of atmospheric formation in celestial bodies. Arimatsu’s team mentioned, “This discovery suggests that traditional ideas about atmospheres forming only around larger planets need revision.”
As scientists look to analyze the atmosphere further, the next steps involve using advanced telescopes. Tracking how the atmosphere’s density changes over time will help determine its origin. If it decreases, the atmosphere might stem from a recent impact. However, if it stays stable, it could mean the object is actively releasing gases.
The findings, published in Nature Astronomy, open up intriguing questions about how small celestial bodies can support atmospheres, shifting our previous assumptions based on size alone.
