Atmosphere Found on Outer Solar System Body: Japan Team

Tokyo, May 5 (Jiji Press)–A thin atmosphere has been found to exist on one of thousands of trans-Neptunian objects, or TNOs, small celestial bodies outside Neptune, the outermost planet in the solar system, a research team including the National Astronomical Observatory of Japan said. It is the first time that an atmosphere has been found on any TNO other than Pluto. The discovery, which was announced on British journal Nature Astronomy on Monday, was made through coordinated observations by Japanese professional and amateur astronomers using small telescopes, according to the team. Temperatures in the outer solar system are minus 220 degrees Celsius or lower, and it had been thought that only nitrogen, methane and carbon monoxide can exist in the form of gas, and that there is almost no atmosphere on the surface of TNOs. While a thin atmosphere has been found only on Pluto, which is about 2,400 kilometers in diameter, it had been believed that smaller TNOs cannot retain atmospheres due to their weak surface gravity. Ko Arimatsu, a researcher at the NAOJ, and others drew up a plan to observe 2002 XV93, one of the TNOs, using telescopes in the central prefecture of Nagano and Kyoto Prefecture, western Japan, on Jan. 10, 2024, when the TNO, which has a diameter of about 500 km and is about 5.5 billion km from Earth, was predicted to block the light from a distant star in a phenomenon known as occultation. They called on astronomers, both professional and amateur, to observe 2002 XV93 together that day. During the occultation, the light from the star would disappear almost instantly if there is no atmosphere on 2002 XV93. If there is an atmosphere, the light would disappear gradually due to refraction. Data from Nagano and Kyoto as well as an observation by Katsumasa Hosoi, an amateur astronomer in Fukushima Prefecture, northeastern Japan, found that the light from the star gradually disappeared, confirming the existence of an atmosphere on the TNO. An analysis of the data also found that the atmospheric pressure on 2002 XV93 is estimated to be 50 to 100 times lower than that of Pluto and five million to 10 million times lower than that of Earth. A possible heat source inside the TNO may have led to the creation of the atmosphere or the atmosphere may have been produced due to the collision of small celestial bodies, according to the research team. The latest discovery of an atmosphere on 2002 XV93 may help “change the image” of the outer solar system, Arimatsu said. END [Copyright The Jiji Press, Ltd.]