Nauru is the world’s smallest island nation, covering only eight square miles in the South Pacific, but in late June, it’s the perfect location for studying Pluto. Two scientists from the Southwest Research Institute (SwRI) in Boulder, Colo., are traveling to ARM’s Tropical Western Pacific site on Nauru Island to observe Pluto and two of its moons during a “stellar occultation.” This event occurs when a body passes between an observer and a distant star. When Pluto and its moons Charon and Hydra block the light from bright stars, scientists are able to gather information about Pluto’s atmospheric temperature and pressure and the moons’ sizes and orbits.

Like Earth, Pluto’s atmosphere consists primarily of nitrogen, but Pluto is so cold that the nitrogen exists both as frozen ice on the surface and as a gas. As the nitrogen ice warms up or cools down, the atmosphere expands or contracts. By studying Pluto’s atmosphere, scientists learn about the interactions of surfaces and atmospheres on nitrogen-covered worlds at the edge of our solar system.

The SwRI scientists are traveling to various locations across the Pacific throughout June. Using a 14-inch portable telescope and specialized cameras, they’ll spend the nights of June 23 and 27 observing the Pluto occultation from the Nauru site. As a global scientific user facility, ARM is uniquely positioned to host this unusual and interesting activity at Nauru.