Catalina Sky Survey team watching 2024 YR4, which has a 2 percent chance to hit planet in 7 years
Back on Christmas Day last year, Earth had another near-miss when a midsized asteroid whizzed past our planet, coming within 828,000 kilometers of bumping into us.
Astronomers give the asteroid, now dubbed 2024 YR4, a 2 percent chance of colliding with the planet on Dec. 22, 2032.
But we're not all going to die, said David Rankin, an astronomer who works with the Catalina Sky Survey atop Mount Lemmon.
"This is definitely nothing to lose sleep over," Rankin said. "You're much more likely to die in a car accident, or probably even by a lightning strike, than you are to die in an asteroid impact."
If 2024 YR4 does hit the planet, "This would not be considered like a dinosaur-type ending event," Rankin added. "That asteroid was 10 kilometers wide, like Mount Everest-sized rock that hit the planet. This is going to be like a more regional, localized threat."
That's not to say 2024 YR4 couldn't cause a lot of damage, depending on where the impact occurred. If it were to hit Earth, Rankin said the impact corridor cuts across the northern part of South America, Sub Saharan Africa and India.
"If it hits over open ocean, maybe there's a possibility of a tsunami," Rankin said. "There's still a lot of modeling that has to be done for that. And if it hits over land, it could cause some serious damage."
2024 YR4 is more of a "stony type" of asteroid made up of silicate rocks and nickel-iron, Rankin said, rather than a solid hunk of metal like the nickel-iron asteroid that forged Meteor Crater near Flagstaff. That meteor did not break up in the atmosphere and left a mile-wide crater that's now a tourist attraction.
If 2024 YR4 were to strike Earth, "the atmosphere will basically flash it into pure energy on the way in, and you'll get this fireball that hits the surface of the ground and just bakes everything around it at like 1,000 degrees."
2024 YR4 is an estimated 40 to 90 meters (or 130 to 300 feet) in diameter, according to the best guess of astronomers.
That puts it in the range of the meteor that exploded over Russia's East Siberia taiga in 1908 in the Tunguska event, knocking down an estimated 80 million trees.
There's still a lot to learn about 2024 YR4, including details about its size, mass and trajectory. Astronomers hope to observe the asteroid with the James Webb Space Telescope in March and will have a chance to see it again when it makes another swing past Earth in December 2028.
2024 YR4 is the latest asteroid to join the list of nearly 40,000 near-Earth asteroids that been detected by NASA.
The Catalina Sky Survey, a branch of the University of Arizona's Steward Laboratory, works with ATLAS, the NASA-funded Asteroid Terrestrial-Impact Last Alert System, a Hawaii-based network of stargazers who watch the skies to detect asteroids that could pose a danger to the planet.
The asteroid was first spotted by ATLAS' Chilean station on Dec. 27. When the team at Catalina Sky Survey looked back at what their instruments had detected that night, they discovered their cameras had also captured images of the asteroid.
Rankin said astronomers estimate they've spotted more than 90 percent of earth-threatening asteroids that are more than 1,000 kilometers across.
"So are we going to be surprised by an asteroid that can end human civilization in the next century?" Rankin said. "No, the odds of that are extremely low, because we found most of the rocks in the size range that could put an end to human civilization."
But smaller ones, such as those in 2024 YR4's range, are a different story.
"When you get down to smaller rocks, the ones that can cause regional destruction, the numbers aren't so pretty," Rankin said. "We're looking at 40 percent down to 140 meters, and then it tapers off very quickly when you get down to the size range that this rock is in, which is in that 40- to 90-meter range."
Many of those asteroids pass Earth in the daytime sky and are not seen by astronomers.
"So can we be surprised by an asteroid from the daytime part of the sky?" Rankin said. "Yes, at any moment that could happen anywhere on the planet, then cause massive devastation, and we would have never seen that asteroid before. That's very possible."