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University of Hawaii astronomers are playing a pivotal role in tracking an asteroid once feared to pose a risk to Earth.

Using telescopes on Maunakea, including the Canada-France-Hawaii Telescope, these scientists have helped refine calculations on the trajectory of asteroid 2024 YR4.

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A UH telescope discovered the “city-killer” size asteroid in December. Recent calculations gave it a 3% probability of colliding with Earth in December 2032, but the newest observations collected Wednesday show that the likelihood has dropped to just 0.28%.

“The atmosphere above Maunakea tends to be very stable, and it enables telescopes to produce very sharp images, sharper than most other observatory locations,” David Tholen, an astronomer at UH’s Institute for Astronomy, said in a press release.

Tholen, along with IfA colleagues Richard Wainscoat and Rob Weryk, analyzed images captured by the CFHT’s MegaCam, a 380 megapixel wide-field camera designed for asteroid tracking and deep-space imaging.

The team’s findings are crucial to NASA’s planetary defense efforts, providing critical data for experts assessing the asteroid’s path.

However, time is running out for ground-based tracking.

“The distance between the Earth and the asteroid keeps increasing, and as that happens, the asteroid gets fainter and fainter, and at some point, it will be too faint to reach with even the largest telescopes we have here on Earth,” Tholen said.

By April, 2024 YR4 will be too distant and faint to detect with Earth-based telescopes.

NASA plans to use the James Webb Space Telescope in May to gather further insights on its size and structure, but the next opportunity to monitor the asteroid from Earth will not come until 2028, when it will again be bright enough for telescopic observations.

Despite the lower impact probability, astronomers remain vigilant. History has demonstrated the destructive power of similar-sized asteroids.

In 1908, a comparable object exploded over Tunguska, Siberia, leveling 1,000 square miles of forest. If an asteroid the size of 2024 YR4 entered Earth’s atmosphere over a populated area, it could generate a powerful airburst capable of breaking windows or causing minor structural damage across an entire city.