Astronomers Discover Trans-Neptunian Object With Atmosphere in Outer Solar System

Astronomers have discovered a small celestial object which measures 310 miles (500 kilometers) in diameter with an atmosphere that exists beyond Neptune's orbit. This body is part of a family of objects called trans-Neptunian objects (TNOs), and has the designation (612533) 2002 XV93. The objects in this group belong to a collection of materials which remained after the solar system formed approximately 4.5 billion years ago.

A Fleeting Star Reveals a Hidden Air

According to the study, this is achieved by a rare stellar occultation that took place when the occulted body passed in front of a star on 10 January 2024 as observed from Japan. Under the leadership of Dr Ko Arimatsu from NAOJ, the team of both professionals and amateurs detected the light of the star dimming slowly, as opposed to instantly disappearing, which indicates the presence of an atmosphere. The pressure on the surface of this exosphere is very low, between 100 and 200 nanobars (that is, 5 and 10 million times less than Earth's atmospheric pressure).

How Did This Atmosphere Form?

That is the core conundrum. Due to the extremely low temperatures, combined with the very weak gravitational force exerted by TNOs, none should be capable of holding onto an atmosphere. It is believed that either a recent comet collision with the TNO freed up the captured gases or that the formation of an ice volcano on the surface is behind the mystery atmosphere's presence. According to astronomer Scott Sheppard, who has spent years studying TNOs, the discovery proves the Kuiper Belt is not a sterile, frozen wasteland but rather an area teeming with life and holding most of the ingredients required for life.