Astronomy Tonight for - 06-22-2025

On June 22, 1978, James Christy, an astronomer at the United States Naval Observatory, made a groundbreaking discovery that would forever change our understanding of the outer solar system. While examining photographic plates of Pluto (which was still considered a planet at the time), Christy noticed an unusual bulge on the edge of Pluto's image. At first, he thought it might be a defect in the photographic plate or a processing error. However, upon closer inspection and comparison with other images, Christy realized he had stumbled upon something extraordinary: Pluto had a moon! This celestial companion was later named Charon, after the mythological ferryman who carried souls across the river Styx to the underworld – a fitting name for the moon of a planet named after the god of the underworld. The discovery of Charon was a astronomical mic drop moment, completely reshaping our view of the outer solar system. It turned out that Charon is unusually large compared to Pluto, with about half the diameter and one-eighth the mass of its parent body. This led to the two bodies being reclassified as a "double dwarf planet system." Charon's discovery also paved the way for further exploration of the Pluto system. In 2015, the New Horizons spacecraft flew by Pluto and Charon, providing us with stunning close-up images and a wealth of data about these distant worlds. So, the next time you're stargazing on a June 22nd, give a little nod to James Christy and his eagle eyes. Thanks to him, we know that even in the coldest, darkest corners of our solar system, no one has to dance alone – even Pluto has a partner!