Free Astronomy Magazine July-August 2026

21 JULY-AUGUST 2026 ASTRO PUBLISHING But astronomers like to expect the unexpected, so they took advantage of a lucky “natural experiment” to look for an atmosphere around a TNO known as (612533) 2002 XV 93 . This object, abbreviated as 2002 XV 93 , has a diameter of approxi- mately 500 km. For reference, Pluto’s diameter is 2,377 km. The orbit of 2002 XV 93 is such that, as seen from Japan, it passed directly in front of a star on January 10, 2024. As the star disappears behind 2002 XV 93 , it might gradually fade, indicating that the light is being at- tenuated as it passes through a thin atmosphere; or it might suddenly wink out as it slips behind the solid S ize comparison of 2002 XV 93 (im- aged by HST), Pluto, and the as- teroid Vesta (which is irregularly shaped with no atmosphere). The atmospheres of 2002 XV93 and Pluto are depicted as a blue glow, brightness exaggerated for visibility. [NASA/HST/Keith S. Noll] Calculations show that the atmos- phere found around 2002 XV 93 is ex- pected to last less than 1000 years unless it is replenished. So it must have been created or replenished re- cently. Observations by the James Webb Space Telescope show no signs of frozen gases on the surface of 2002 XV 93 that might sublimate to form an atmosphere. One possibility is that some event brought frozen or liquid gases from deep inside the TNO to the surface. Another possibil- ity is that a comet crashed into 2002 XV 93 , releasing gas that formed a temporary atmosphere. Further ob- servations are needed to distinguish between these two scenarios. surface of the TNO. A team of professional and amateur astronomers, led by Ko Arimatsu at NAOJ Ishigakijima Astronomical Ob- servatory, observed the star as 2002 XV 93 passed in front of it from multi- ple sites in Japan. The obtained data are consistent with attenuation by an atmosphere. !