Japanese Astronomers Detect Thin Atmosphere on Small Trans-Neptunian Object

Japanese astronomers have detected a thin atmosphere around a small celestial body in the outer solar system, according to a study published May 4 in the journal Nature Astronomy. The object, temporarily named (612533) 2002 XV93, measures roughly 310 miles in diameter.

Researchers said the body is much smaller than what was previously thought necessary to retain an atmosphere in the region beyond Neptune. Pluto had been considered the only body beyond Neptune with an atmosphere. The new observations indicate that at least one smaller trans-Neptunian object also possesses a thin atmosphere, possibly composed of methane, nitrogen or carbon monoxide.

The atmosphere is estimated to be 5 to 10 million times thinner than Earth's. It surrounds a body located in the Kuiper Belt, a region of icy objects that are ancient remnants from the formation of the solar system. Most trans-Neptunian objects are considered too cold and lacking sufficient gravitational pull to sustain an atmosphere.

The researchers used ground-based telescopes in Japan to observe the object as it passed in front of a distant star, a technique that allowed them to detect the atmosphere.

The researchers proposed two possible origins for the atmosphere. One is that a cosmic event brought frozen or liquid gases from inside the body to the surface. The other is that a comet impact released gases that formed a temporary atmosphere. The discovery raises questions about when and how the atmosphere formed and how it has been maintained.

The team called for further observations to better characterize the atmosphere and resolve those questions. Trans-Neptunian objects occupy a donut-shaped region known as the Kuiper Belt. These bodies do not meet the criteria to be classified as planets.