New algorithm hunts for potentially hazardous asteroids and has already found one

A new study from the University of Washington represents a major advance in asteroid detection. An algorithm developed by the team – known as HelioLinc3D – has made its first discovery of a “potentially hazardous” asteroid.

This term is used for asteroids that orbit close to Earth, requiring vigilant observation by scientists to monitor any threat they may pose to our planet.

Engineered to discover near-Earth asteroids, HelioLinc3D was intended for use in the upcoming 10-year night sky survey by the Vera C. Rubin Observatory. The algorithm’s initial trial run with the ATLAS survey in Hawaii, however, resulted in the detection of a roughly 600-foot-long asteroid, which was named 2022 SF289.

The asteroid, although designated as potentially hazardous, poses no immediate risk to Earth. Nevertheless, this discovery represents an important milestone, as it validates the capability of HelioLinc3D to detect near-Earth asteroids using fewer and more scattered observations than the methods currently in use.

Rubin scientist Ari Heinze, the principal developer of HelioLinc3D, emphasized the significance of the discovery. “By demonstrating the real-world effectiveness of the software that Rubin will use to look for thousands of yet-unknown potentially hazardous asteroids, the discovery of 2022 SF289 makes us all safer,” said Heinze.

Potentially hazardous asteroids 

Tens of millions of rocky bodies populate the solar system. These include tiny asteroids only a few feet across to dwarf planets the size of our moon. These remnants of an era over four billion years ago still orbit the sun today, and their varied paths provide scientists with a wealth of information.

While many of these bodies remain far from us, we categorize a considerable number as near-Earth objects, or NEOs.

The ones whose trajectories bring them within 20 lunar distances, or about 5 million miles of Earth, are of particular interest to scientists. To safeguard against the potential catastrophe of a collision with Earth, scientists meticulously track these “potentially hazardous asteroids” (PHAs).

Specialized telescope systems like the NASA-funded ATLAS survey commonly track potentially hazardous asteroids. ATLAS is administered by a team at the University of Hawaii’s Institute for Astronomy. 

Scientists use these systems to capture images of certain sky regions at least four times nightly, identifying new asteroids by observing points of light that move unambiguously in a straight line across the image series.

This method has been successful in identifying about 2,350 potentially hazardous asteroids. However, scientists estimate that at least twice that number remain undiscovered.

Focus of the research 

By early 2025, the Vera C. Rubin Observatory is expected to boost the PHA discovery rate dramatically. Situated in the Chilean Andes, the observatory is funded primarily by the National Science Foundation and the Department of Energy.

It is equipped with a massive 8.4-meter mirror and a 3,200-megapixel camera. Its unique ability to scan the sky twice per night will significantly outpace the four scans per night by current telescopes.

However, this revolutionary observing pattern necessitated the development of a new kind of discovery algorithm. Rubin’s solar system software team at the University of Washington’s DiRAC Institute created HelioLinc3D. The team worked in collaboration with Smithsonian senior astrophysicist Matthew Holman and Siegfried Eggl from the University of Illinois Urbana-Champaign.

Remarkable results

The team initially tested HelioLinc3D using data provided by lead ATLAS astronomers John Tonry and Larry Denneau. On July 18, 2023, the algorithm pinpointed its first PHA: 2022 SF289. 

Despite ATLAS imaging the asteroid as early as September 19, 2022, from a distance of 13 million miles from Earth, conventional methods still failed to detect it.

“Any survey will have difficulty discovering objects like 2022 SF289 that are near its sensitivity limit, but HelioLinc3D shows that it is possible to recover these faint objects as long as they are visible over several nights,” said Denneau. He noted that the successful discovery of the asteroid essentially gives them a “bigger, better telescope.”

Unrecognized observations 

Furthermore, 2022 SF289 went unnoticed by other surveys due to its path across the star-dense backdrop of the Milky Way. But now, equipped with the knowledge of where to look, observations from Pan-STARRS and Catalina Sky Survey quickly confirmed the discovery. 

The team also utilized the B612 Asteroid Institute’s ADAM platform to recover further unrecognized observations by the NSF-supported Zwicky Transient Facility telescope.

The detected asteroid, 2022 SF289, falls under the classification of an Apollo-type NEO. Its closest approach brings it within a mere 140,000 miles of Earth’s orbit, closer than the moon. However, despite the proximity, projections indicate that it poses no danger of impacting Earth for the foreseeable future.

Promise of a new era

With over 2,350 known potentially hazardous asteroids and an estimated 3,000 or more yet to be discovered, the unveiling of the Rubin Observatory and the deployment of HelioLinc3D in less than two years is eagerly anticipated. 

Rubin scientist Mario Jurić is the director of the DiRAC Institute, professor of astronomy at the University of Washington and leader of the team behind HelioLinc3D.

“This is just a small taste of what to expect with the Rubin Observatory,” said Jurić. “But more broadly, it’s a preview of the coming era of data-intensive astronomy. From HelioLinc3D to AI-assisted codes, the next decade of discovery will be a story of advancement in algorithms as much as in new, large, telescopes.”

More about potentially hazardous asteroids

Potentially Hazardous Asteroids (PHAs) are celestial objects that come into close proximity with Earth and, due to their size and trajectory, could potentially cause significant damage in the event of an impact.

Classification

NASA classifies an asteroid as potentially hazardous if its orbit intersects Earth’s orbit at a distance less than or equal to 7.5 million kilometers (approximately 4.6 million miles), and if the asteroid is larger than 140 meters (approximately 460 feet) in diameter.

While these asteroids pose a theoretical risk to our planet, most of them will never actually come into collision with Earth.

Identification and Tracking

Astronomers locate and track PHAs using both ground-based and space-based telescopes. They feed collected data into models that calculate the asteroid’s orbit, size, and composition.

Observations over time help to refine these models and predictions. NASA’s Center for Near-Earth Object Studies (CNEOS) manages this process, with contributions from observatories and space agencies worldwide.

Known PHAs

As of 2023, scientists have identified more than 20,000 PHAs. However, this number represents a fraction of the total estimated PHAs. Ganymed, an asteroid measuring roughly 32 kilometers (20 miles) in diameter, holds the title of the largest known potentially hazardous asteroid.

Another well-known PHA is Apophis, which gained notoriety due to its initially high impact probability in 2029 and 2036, though later data eliminated these risks.

Impact Risks and Mitigation

While the chances of a significant asteroid impact are low, the potential consequences warrant careful monitoring. An asteroid strike could cause catastrophic damage, potentially leading to mass extinction events similar to what happened 65 million years ago during the Cretaceous–Paleogene extinction event.

Several strategies exist for deflecting a PHA on a collision course with Earth. Kinetic impactors involve crashing a spacecraft into the asteroid to alter its trajectory. Gravity tractors would slowly tug the asteroid off course using the gravitational attraction between the spacecraft and the asteroid. Nuclear explosions, while controversial, could also serve as a last-ditch effort to change the asteroid’s course or fragment it.

Future prospects

The future of PHA tracking and mitigation involves improvements in technology and international cooperation. New projects like NASA’s Near-Earth Object Surveillance Mission and the European Space Agency’s Hera mission aim to enhance our ability to detect, track, and understand PHAs. They will also test our capacity to deflect asteroids, contributing to our preparedness for potential future threats.

Potentially Hazardous Asteroids represent a low-probability but high-consequence risk to life on Earth. As our understanding and technology continue to advance, our capacity to mitigate this threat improves. Continued vigilance and scientific inquiry are the keys to maintaining Earth’s safety in an active cosmic neighborhood.

Video Credit: DiRAC Institute, University of Washington

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