Last night, I joined several teams of scientists as they chased Pluto’s shadow across the southern Pacific ocean. We were riding aboard NASA’s flying infrared telescope, SOFIA, and needed to get that Boeing 747 to the exact right place at the exact right time.

Just before 5 a.m. New Zealand time, Pluto would slide in front of a bright star in the constellation Sagittarius and cast a Pluto-size shadow along a swath of Earth. Called an occultation, the relatively rare celestial alignment lets astronomers use the distant star’s light to probe the structure of Pluto’s atmosphere, which has been behaving a bit oddly since its discovery in 1988.

This would be the brightest star Pluto had yet occulted