A little-known population of asteroids sharing Venus's orbit has intrigued scientists. Their unstable trajectories could bring them closer to our planet.
These celestial bodies, called co-orbitals or trojans, accompany Venus in its revolution around the Sun. Although their existence has been known for years, two recent studies reveal that some could, in the very long term, adopt orbits bringing them near Earth. No immediate danger is expected, but this research highlights the need for better monitoring of these elusive objects.
Unpredictable orbits
Venus's co-orbital asteroids move in gravitationally stable zones called Lagrange points. According to simulations, their trajectories can become unstable over timescales exceeding 12,000 years. Some then develop elongated orbits, increasing their chances of crossing Earth's path.
Among the 20 identified co-orbitals, three could come very close to our planet. These projections, published in
Icarus, involve asteroids measuring 300 to 400 meters (1,000 to 1,300 feet) in diameter. Their size classifies them as potentially hazardous objects, but none pose a threat for several millennia.
Gravitational disturbances make their trajectories chaotic in the long term. A second study, currently under peer review, confirms this instability even for initially low-eccentricity orbits.
A detection challenge
Spotting these asteroids remains difficult due to their proximity to the Sun. Ground-based telescopes can only observe them briefly at dusk or dawn. Solar glare and atmospheric distortion severely limit their detection.
The future Vera Rubin Observatory in Chile could revolutionize this search. Its wide field of view and sensitivity may uncover thousands of new asteroids, including those hidden near Venus. An infrared space telescope, like NASA's NEO Surveyor, would complement these observations by avoiding atmospheric interference.
These tools will provide a better assessment of the actual risks. For now, scientists stress there is no short-term threat.
Article author: Cédric DEPOND