WASHINGTON: A colossal explosion in the sky, unleashing energy hundreds of times greater than the Hiroshima bomb. A blinding flash nearly as bright as the Sun. Shockwaves powerful enough to flatten everything for miles.

It may sound apocalyptic, but a newly detected asteroid nearly the size of a football field now has a greater than one per cent chance of colliding with Earth in about eight years. Such an impact has the potential for city-level devastation, depending on where it strikes. Scientists aren’t panicking yet, but they are watching closely. “At this point, it’s ‘Let’s pay a lot of attention, let’s get as many assets as we can observing it,’” Bruce Betts, chief scientist of The Planetary Society, said.

Rare finding

Dubbed 2024 YR4, the asteroid was first spotted on Dec 27, 2024, by the El Sauce Observatory in Chile. Based on its brightness, astronomers estimate it is between 130 and 300 feet (40-90 meters) wide. By New Year’s Eve, it had landed on the desk of Kelly Fast, acting planetary defence officer at US space agency Nasa, as an object of concern.

“You get observations, they drop off again. This one looked like it had the potential to stick around,” she said. The risk assessment kept climbing, and on Jan 29, the International Asteroid Warning Network (IAWN), a global planetary defence collaboration, issued a memo.

According to the latest calculations from Nasa’s Jet Propulsion Laboratory, there is a 1.6 percent chance the asteroid will strike Earth on Dec 22, 2032. If it does hit, possible impact sites include over the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia, the IAWN memo states.

2024 YR4 follows a highly elliptical, four-year orbit, swinging through the inner planets before shooting past Mars and out toward Jupiter. For now, it’s zooming away from Earth — its next close pass won’t come until 2028.

“The odds are very good that not only will this not hit Earth, but at some point in the next months to few years, that probability will go to zero,” said Betts. A similar scenario unfolded in 2004 with Apophis, an asteroid initially projected to have a 2.7pc chance of striking Earth in 2029. Further observations ruled out an impact.

Destructive potential

The most infamous asteroid impact occurred 66 million years ago, when a six-mile-wide space rock triggered a global winter, wiping out the dinosaurs and 75pc of all species. By contrast, 2024 YR4 falls into the “city killer” category.

“If you put it over Paris or London or New York, you basically wipe out the whole city and some of the environs,” said Betts.

The best modern comparison is the 1908 Tunguska Event, when an asteroid or comet fragment measuring 30-50 meters exploded over Siberia, flattening 80 million trees across 770 square miles (2,000 square kilometers).

Like that impactor, 2024 YR4 would be expected to blow up in the sky, rather than leaving a crater on the ground. “We can calculate the energy… using the mass and the speed,” said Andrew Rivkin, a planetary astronomer at Johns Hopkins Applied Physics Laboratory.

Published in Dawn, February 2nd, 2025