Unistellar Observers Catch NASA’s Lucy Mission Target Eurybates Over France

On October 23, the shadow of an asteroid passed very briefly over France, cutting a path through the country’s center from north to south. There to see it were dedicated Citizen Astronomers, who pointed their Unistellar telescopes skyward as part of a partnership between Unistellar and the French Astronomy Association (AFA).

The asteroid in question was Eurybates, an asteroid that’s a target of NASA’s upcoming Lucy mission. In 2027, the Lucy spacecraft will arrive at the Trojan asteroids, a population of asteroids that follow Jupiter’s orbit around the Sun, including Eurybates. But there’s lots for scientists to do before that happens, including getting better data on Lucy’s targets. Citizen Astronomers can help with this preparation by watching for the asteroid as it passes in front of a star and briefly blocks its light, an event known as an occultation. These quick glimpses are enough to give astronomers information on an asteroid’s size, shape and orbit, all critical pieces of information for the Lucy mission.

An asteroid occultation occurs when a nearby asteroid briefly blocks the light from a distant star.

Unistellar and the AFA mobilized hundreds of observers from across France, and the rest of Europe, to participate in the observation of Eurybates, which turned out to be one of their largest occultation observing campaigns yet! Their efforts led to several positive detections of the occultation with Unistellar telescopes. Scientists are currently analyzing the observations to potentially reveal the shape of the asteroid. Preliminary results include a “double occultation”, which may indicate that Eurybates is bean-shaped or has a large crater on its surface. Once fully processed, the data will be shared with NASA scientists from the Lucy mission to aid their efforts.

Patrice Girard with his Unistellar telescope.

Olivier Clerget with his Unistellar telescope.

Laurent Runigo with his Unistellar telescope

French observers also had the rare opportunity to hunt for an occultation by Queta, the only known moon of Eurybates. Scientists suspected that Queta might obscure a star shortly before or after Eurybates’ occultation, and because the moon’s size is not well known, they could not be sure exactly where Queta’s shadow would fall and if it would even be detectable. The observations of Queta are still being analyzed in hopes that the data will reveal an occultation.

Occultation of Eurybates with an eVscope from France.

The Lucy mission launched in October 2021, and will fly by six Jupiter Trojans, including Eurybates and Queta, during its journey to study these still-mysterious asteroids. The Trojans, which orbit in two distinct groups, hail from the Solar System’s early days, so they function like time capsules that help scientists study that time. With their observations of Eurybates and Queta, Citizen Astronomers directly contributed to a NASA mission that may help unravel the secrets of our beginnings.

We’ll be making many more asteroid occultation observations in the lead-up to the Lucy mission’s arrival, and anyone with an eVscope can join in! Learn more about asteroid occultations on the Unistellar website, including predictions for occultations that will be visible near you.