In the future, we will likely encounter more asteroids like 2024 YR4. (Image credit: Christoph Burgstedt/Science Photo Library via Getty Images)
Asteroid 2024 YR4 went from potential city-killer to almost guaranteed close caller this week, as the odds of it hitting Earth in 2032 first rose, then plummeted in a matter of days. Here's what happened and why it matters.
Asteroid 2024 YR4 is about 180 feet (55 meters) in diameter and is capable of releasing 500 times more energy than the atomic bomb that destroyed Hiroshima. So a little worry was natural on Tuesday (Feb. 18), when the probability of YR4 hitting Earth rose to 3.1 percent — the highest impact probability recorded by NASA for an object of its size or larger.
Fortunately, this record probability was short-lived, and the chances of an impact soon dropped to 1.5%, and at the time of writing, are already 0.28%. None of this came as a surprise to astronomers.
The most likely scenario for 2024 YR4 has always been that it will fly past us on its closest approach to Earth in 7 years. Although astronomers have known about 2024 YR4 since last year, the uncertainty in its orbital path meant they couldn’t — and still can’t — rule out the possibility of an impact. Small changes in that uncertainty have translated into changing odds, sparking interest around the world.
“Astronomers don’t and can’t hide their findings because the sky is open to all,” Richard Binzel, creator of the Torino Asteroid Impact Hazard Scale and a professor of planetary science at MIT, told Live Science in an email. “So when we discover one of these future visitors that may someday be on the brink of disaster, the scientific method of slowly and carefully measuring to get answers is brought to the public domain.”
What is the hazard level of asteroid 2024 YR4?
To assess the threat posed by asteroids and comets, researchers use the Binzel Asteroid Impact Hazard Scale. The Torino scale consists of 11 levels, ranging from 0 (no danger) to 10 (global catastrophe).
In January 2025, 2024 YR4 reached Level 3 after scientists determined that it had a greater than 1% chance of colliding with Earth. Level 3 asteroids can cause “localized destruction,” consistent with 2024 YR4's potential to destroy a city.
However, even as 2024 YR4's odds increased to more than 3% — and decreased to 1.5% — it remained at level 3. Binzel noted that it is “perfectly natural” for 2024 YR4's impact odds to “fluctuate a little bit.” Still, level 3 means that scientists expect the asteroid to eventually show a 0% impact chance with further observations.
Darker skies have given astronomers better conditions to observe the asteroid in recent days, following a week of limited visibility during February’s full moon. Clearer nighttime observations on Feb. 19 and 20 allowed NASA to refine YR4’s impact probability to 1 in 360, or 0.28%, according to the NASA Planetary Defense blog.
Sourse: www.livescience.com
