An international study spearheaded by researchers at São Paulo State University (UNESP) in Brazil has unveiled a significant yet previously overlooked threat: asteroids that share an orbit with Venus. Unique in their trajectory, these asteroids may completely evade detection by current observational techniques due to their celestial positioning. While no such objects have been detected to date, their potential to collide with Earth within a few thousand years poses a risk that could result in catastrophic destruction in densely populated urban areas.
The study’s lead author, astronomer Valerio Carruba, emphasized that this research highlights the existence of a cohort of potentially hazardous asteroids that existing telescopes are incapable of identifying. These objects orbit the Sun but are distinct from the well-known Asteroid Belt that lies between Mars and Jupiter. Instead, they exist much closer to Earth in resonance with Venus, making them increasingly elusive to current observation efforts. This inability to observe them could mean that these asteroids pose a genuine threat of collision with our planet in the far future, Carruba cautioned.
An article detailing these findings has been published in the journal Astronomy & Astrophysics. Through analytical modeling and long-term numerical simulations, Carruba and his team explored the dynamics of these asteroids, aiming to assess their potential risks in relation to Earth. Their work sheds light on the so-called “Venusian co-orbital asteroids,” which, unlike other asteroids, orbit the Sun in unique patterns that mirror Venus’s own orbit around the star.
These asteroids, classified as “Venusian co-orbitals,” share the same orbital region and period as Venus but do not orbit the planet itself. Carruba elucidated that these asteroids have a 1:1 resonance with Venus, indicating that they complete a full orbit around the Sun in synchronization with the planet. This intricate dance of celestial mechanics makes these bodies both fascinating and formidable.
What makes Venusian co-orbitals particularly worrying is their highly eccentric orbits. Current knowledge indicates that these objects are less stable compared to the familiar Jupiter Trojans. They go through alternating orbital configurations in cycles that average about 12,000 years. During these cycles, an asteroid may find itself in a stable position near Venus and, in a subsequent phase, venture dangerously close to Earth’s orbit. Carruba highlighted that at certain transition points, these asteroids could approach extremely close distances to Earth, with the potential to cross our orbital path altogether.
The study identifies a clear observational bias concerning these asteroids. The existing catalog comprises only 20 Venusian co-orbital asteroids, most demonstrating eccentricities exceeding 0.38. Such a high eccentricity means these objects operate in orbital regions that take them farther from the Sun and thereby become easier targets for observation. However, computer models predict a much larger population of less eccentric asteroids, lurking invisibly closer to the Sun, and consequently remaining undetected from Earth. This intriguing absence of lower eccentricity objects denotes the limitations of our current observational capabilities.
Eccentricity serves as a vital measure of orbital shape, with values ranging from 0—indicating a circular orbit—to approaching 1 for highly elliptical orbits. For context, Earth’s orbit has an eccentricity of roughly 0.017, making it nearly circular. In stark contrast, the known Venus co-orbital asteroids possess high eccentricities, indicative of their highly elongated paths. Asteroids with lower eccentricities, however, remain more closely tethered to their average orbits, rendering them nearly invisible when in close proximity to the Sun.
During simulated experiments with theoretical asteroids, researchers pinpointed regions where these objects could approach Earth alarmingly closely. Some of the simulated asteroids demonstrated minimum distances around 5×10^−45 astronomical units. This minuscule distance translates statistically to almost certain impacts over a millennial timescale. Carruba noted that researchers might be missing asteroids roughly 300 meters wide, large enough to create massive craters—up to 4.5 kilometers across—and unleash energy on par with hundreds of megatons upon impact. The implications for urban environments from such an event are staggering, as concentrated damage in populous regions could lead to widespread devastation.
The potential for detection of these asteroids from Earth was examined, particularly with the newly inaugurated Vera Rubin Observatory (previously known as the Large Synoptic Survey Telescope) in Chile. However, the study’s simulations reveal that even the brightest Venusian co-orbital asteroids would only be observable for one to two weeks when above 20 degrees on the horizon. This limited visibility window interspersed with lengthy intervals of non-observation makes it exceedingly challenging to detect these asteroids using standard observational programs at the Vera Rubin Observatory.
An alternative approach to tackle this invisible threat includes employing space telescopes specifically targeting regions near the Sun. Proposed missions such as NASA’s Neo Surveyor, along with China’s Crown mission, could feasibly identify asteroids positioned at these low solar elongations from Venus’s orbit, offering more thorough and continuous coverage. Carruba urged that planetary defense strategies must extend beyond just tracking observable objects and must incorporate those that remain hidden from our current view.
Historically, the origins of asteroids have been attributed to the fragmentation of a theorized Earth-like planet following an impact. The prevailing theory about the objects populating the Asteroid Belt, meanwhile, indicates that these remnants date back to the Solar System’s formation. These rocky bodies originated as planetesimals, unable to coalesce into full-fledged planets due to the gravitational disturbances caused by Jupiter. Consequently, the Asteroid Belt is thought of as a relic of the protoplanetary disk, preserving various evolutionary stages and compositions of planetary building blocks.
As for the Venusian co-orbitals, they are believed to have originated in the Main Belt. Gradually, through intricate gravitational interactions, primarily influenced by Jupiter and Saturn, they were redirected to more internal orbits. This migration process leads to a temporary resonance with Venus, though these captures are short-lived, averaging around 12,000 years. Over time, these asteroids could shift trajectories closer to Earth or may even be expelled from the Solar System altogether.
This research, conducted by the Orbital Dynamics and Planetology Group (GDOP) at UNESP, received foundational support from a scholarship granted by FAPESP (São Paulo Research Foundation) to Gabriel Antonio Caritá, a doctoral student at the National Institute for Space Research. The findings from this exploration reveal the urgent need for advanced observational strategies to identify the threats from the cosmos that elude our current detection capabilities. Global awareness and action are crucial as we navigate the complexities of defending our planet from potential asteroid impacts in the future.
Subject of Research: Venusian co-orbital asteroids and their potential threat to Earth
Article Title: The invisible threat – Assessing the collisional hazard posed by undiscovered Venus co-orbital asteroids
News Publication Date: 30-Jun-2025
Web References: www.fapesp.br/en
References: Astronomy & Astrophysics
Image Credits: [As per source]
Keywords
Asteroids, Venus, orbital dynamics, planetary defense, Earth impact, astronomical observation.
