Gaia has previously examined asteroids known to possess moons, termed 'binary asteroids,' and confirmed the presence of these tiny satellites using its highly accurate astrometric data. However, this recent discovery marks a significant advance, proving that Gaia can also conduct 'blind' searches to detect new binary asteroid candidates.

"Binary asteroids are difficult to find as they are mostly so small and far away from us," says Luana Liberato of Observatoire de la Cote d'Azur, France, lead author of the new study. "Despite us expecting just under one-sixth of asteroids to have a companion, so far we have only found 500 of the million known asteroids to be in binary systems. But this discovery shows that there are many asteroid moons out there just waiting to be found."

If confirmed, this new observation would add 352 more binary candidates to the current count, nearly doubling the known population of asteroids with moons.

Gaia's Role as an Asteroid Explorer
Asteroids are key to understanding the formation and evolution of our Solar System. Binary asteroids, in particular, offer unique opportunities to study the interactions, collisions, and formations of celestial bodies.

Since its launch in 2013, Gaia has made significant contributions to asteroid science, leveraging its all-sky scanning capabilities. In its third data release (DR3), Gaia precisely mapped the positions and trajectories of over 150,000 asteroids. This level of precision allowed scientists to identify asteroids with a characteristic 'wobble,' indicative of a companion's gravitational pull, similar to the mechanism used in binary star systems. Gaia also gathered extensive data on asteroid composition, producing the most extensive collection of asteroid reflectance spectra to date.

The orbits identified in Gaia's DR3 were refined to be 20 times more accurate in the mission's Focused Product Release last year. Further asteroid discoveries are anticipated in Gaia's upcoming data release 4, expected no earlier than mid-2026.

"Gaia has proven to be an outstanding asteroid explorer, and is hard at work revealing the secrets of the cosmos both within and beyond the Solar System," says Timo Prusti, Project Scientist for Gaia at ESA. "This finding highlights how each Gaia data release is a major step up in data quality, and demonstrates the amazing new science made possible by the mission."

Future Exploration of Binary Asteroids
ESA's forthcoming Hera mission, scheduled to launch later this year, will further investigate binary asteroids. Hera will follow up on NASA's DART mission, which intentionally collided with Dimorphos, a moonlet orbiting the asteroid Didymos, in 2022 as part of an asteroid deflection experiment. Hera will be the first mission to rendezvous with a binary asteroid system, providing a post-impact analysis of Dimorphos.

Gaia played a role in observing the shadow cast by Didymos as it passed in front of distant stars in 2022, using a method called stellar occultation. This technique has been greatly enhanced by Gaia's precise asteroid orbits and star maps, underscoring the mission's significant contributions to Solar System research.

Research Report:Binary asteroid candidates in Gaia DR3 astrometry

Related Links
Gaia Space Telescope
Asteroid and Comet Mission News, Science and Technology