In 1973, astronomer Gordon Taylor of the Royal Greenwich Observatory had predicted an occultation of the star SAO 158687 by Uranus, to happen in March 1977. Cornell University astronomer James Elliot convinced NASA to use the Kuiper Airborne Observatory – a converted jet plane carrying a 0.9-meter telescope – to view the event. Along with his multi-institutional team, he planned to use the occultation to study Uranus’ atmosphere and measure its diameter.
On March 10, 1977, the team boarded the plane, which cruised over the Indian Ocean and above Earth’s atmosphere. An error had been discovered in Taylor’s prediction a few months earlier, and, concerned that they’d miss the event, Elliot decided to start the photometer recording 41 minutes early. Serendipitously, this early start allowed for a remarkable discovery: Just six minutes after the recording began, there was a dip in starlight along the planet’s edge that the scientists at first theorized may be atmospheric clouds, equipment error, or moons. But when the star emerged from behind Uranus, another set of drops in starlight on the other side of the planet perfectly mirrored the first set. The lack of randomness proved the structures were rings – five in all. Future study would bring that total to 11.
