Feeling lucky? Astronomers say that a newly identified space rock, potentially as big as a football field, has a better than 1% chance of crashing into Earth on Dec. 22, 2032.
Those odds may seem pretty good (assuming you're hoping for a miss), but consider this: The International Warning Asteroid Network (IAWN), a global collaboration started in 2013 to monitor and track space objects that could impact Earth issued its first-ever Potential Asteroid Impact Notification for the asteroid, known as 2024 YR4, IAWN Manager Tim Spahr says.
The notification is meant to put the astronomical community on alert to collect as much information as possible on the near-Earth object (NEO) in question.
"Hitting the 1% impact probability is a rare event indeed," Spahr says.
How likely is it to hit?
When IAWN issued its notification on Jan. 29, it reported a 1.3% chance of 2024 YR4 impacting Earth in 2032, based on data from the NASA JPL Center for NEO Studies (CNEOS) and its European counterpart. But, as of Friday, that probability had gone up a bit, to 1.6%.
And time is running out to refine calculations for its orbit and either rule in or rule out an impact, CNEOS Director Paul Chodas says.
"We need larger and larger telescopes to observe this object. By mid-April, he says, "it will be too faint to be detected."
After that, the next opportunity to study it won't come around again until 2028.
Although the current odds look like a 1 in 63 chance of a direct hit, there's still a much better chance of a miss, Chodas stresses.
The way the probability of an impact is determined is much like how the National Weather Service determines the chances that a hurricane will make landfall.
"It's kind of analogous to having a major city such as New Orleans in the cone of uncertainty of a hurricane," Chodas says.
Still, as astronomers further refine the accuracy of their orbital calculations for 2024 YR4, their odds of an Earth strike "could fall to zero almost any day now," he says. "But we don't know that."
Kelly Fast, the acting planetary defense officer for NASA's Planetary Defense Coordination Office, thinks it's important to keep perspective.
"The worldwide community is watching this and taking notice that it's reached this threshold," she says.
"We do want to keep an eye on it. We do take it seriously, but we want to put it in perspective ... There's still a very low probability that it would even impact the Earth at all."
How big is it and how much damage could it do?
The asteroid 2024 YR4 is big, but it's certainly no dinosaur killer. It could cause considerable localized damage were it to impact a populated area.
To rate its destructive potential, astronomers use something called the Torino Scale. CNEOS currently ranks the asteroid a 3 on a scale from 0 to 10. "That does not happen very often," Chodas says. In fact, nothing compares to it since Apophis, a cruise-ship sized asteroid discovered in 2004. It was initially thought to have a 2.7% chance of hitting Earth in 2029, but that probability was later downgraded. In 2021, astronomers said the Earth was safe from Apophis for at least another 100 years.
If 2024 YR4 hit above a city, it "would definitely break windows," says Anne Virkki, a research fellow at the University of Helsinki. Virkki used radar to track near Earth objects at the Arecibo Observatory in Puerto Rico until the 900-ton equipment platform above the main radio telescope there dramatically collapsed in 2020, destroying the instrument.
To figure out how large an asteroid is, astronomers rely on the brightness of the object as a yardstick. Brighter objects are bigger. They place upper and lower limits on size in part because it's not easy to tell how reflective an asteroid might be.
"You can estimate the size based on the brightness observed without knowing precisely how reflective it is ... but there is still some constraint to how reflective asteroids are in general," Virkki says.
In the case of 2024 YR4, astronomers think it is between 40 meters and 90 meters (130 feet to about 300 feet) in diameter. By comparison, the meteor that hit Chelyabinsk, Russia on Feb. 15, 2013, was estimated to be about half that size (17 to 20 meters or 56 to 66 feet) in diameter. The Chelyabinsk object injured some 1,500 people and caused damage to thousands of buildings across several cities.
The energy released over Chelyabinsk was estimated to be equivalent to about 500 kilotons of TNT — about 30 times more than the Hiroshima atomic bomb. If 2024 YR4 hit, it could be more like 8 to 10 megatons, says Carson Fuls, director of the Catalina Sky Survey at the University of Arizona. A blast wave from such an impact would have a radius of several miles.
IAWN's notification says that in the event it did hit Earth, the "impact risk corridor" extends "across the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia."
That includes a lot of ocean, Fuls notes.
"We have had 8 to 10 megaton nuclear tests in the Pacific and that did not create a worldwide tsunami or anything close to that."
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