As NASA‘s Juno flew around Jupiter last week, the spacecraft snapped a photo of an object before it could make a clean getaway.
That clunky, bumpy thing at the far right edge of the frame is Thebe, the second largest of the gas giant planet’s inner moons. The rarely photographed Jovian world was caught on camera May 1, during a close pass. (It’s actually not quite clear whether Juno saw it coming or going.)
Though the mission’s JunoCam takes most of the stunning imagery from Jupiter’s system, this picture came from the little-known Stellar Reference Unit instrument. The spacecraft was just 3,100 miles away from Thebe in space when it took the portrait. Each pixel represents just under 2 square miles.
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“While the SRU’s primary function is to image star fields for navigation, its high sensitivity in low-light conditions makes it a powerful secondary science instrument,” according to NASA.
As of the latest count, Jupiter has a bevy of 115 moons. But unlike the large Galilean moons that astronomers have known since the 17th century, Thebe is a modern-day discovery. Scientists first learned of its existence during the Voyager 1 mission in 1980. The moon is one of four small natural satellites that circle Jupiter inside the orbit of Io, a larger tortured world with active volcanoes.
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Thebe sits at the outer edge of Jupiter’s so-called “gossamer” rings and is believed to play a crucial role in their formation. Scientists think these fainter rings are the product of meteors slamming into Thebe and neighboring moon Amalthea. The impacts are thought to then cause rocks and dust to spray into space around the planet.
The little-known Stellar Reference Unit, an instrument that helps NASA navigate Juno, took the image of Thebe.
Credit: NASA / JPL-Caltech infographic
Thebe, named after one of Zeus’ nymph lovers in Greek mythology, is predominantly red and only about 60 miles wide. Its most distinctive feature is a huge central depression, known as Zethus crater, on the far side of the moon. It spans almost half the width of the moon itself.
Despite its diminutive size, Thebe is built for speed. At a distance of 138,000 miles from Jupiter, it zooms around the planet every 16 hours. That’s fitting for an image whose target looks like it’s sprinting away.
As of 2026, the spacecraft has orbited Jupiter for nearly a decade. It’s studying the origin and evolution of the gas giant planet and its network of moons and dust rings.
During Juno’s primary mission, the spacecraft collected data on Jupiter’s atmosphere and interior. Among its discoveries was finding that the planet’s atmospheric weather layer extends way beyond its water clouds.
After completing 35 orbits, the spacecraft transitioned to looking at the entire system around Jupiter. While the JunoCam has been responsible for many key observations, the SRU instrument has made its own discoveries, such as the “shallow lightning” in Jupiter’s atmosphere.
The extended mission will continue until the spacecraft dies. Though Juno will eventually fall toward Jupiter as its trajectory degrades, NASA says it poses no risk of crashing into or contaminating any of the moons, some of which could be habitable worlds.
