how big is 2024 yr4?
we’re not sure. “when they’re first discovered, they’re just points of light,” says chodas. it could be as small as 35 metres across, or as large as 90 metres. additional study will narrow that down as well.
this handout picture provided by nasa on jan. 31, 2025, shows asteroid 2024 yr4 as observed by the magdalena ridge 2.4-metre telescope at the new mexico institute of technology on jan. 27, 2025.
nasa
what would happen if it struck earth?
it would be bad, but it would not be catastrophic. chodas says the asteroid that exploded over chelyabinsk in russia in 2013 was about 20 metres wide and produced an explosion of about 400 kilotons, equal to about 25 hiroshima bombs.
“that sounds like a lot, but it’s high in the atmosphere,” he says. “it produces a blast wave. it broke a lot of windows, some walls and doors caved in, but really, very few casualties.”
if yr4 were twice the size of the chelyabinsk asteroid, that would mean almost 10 times as much energy. it could flatten a city, were it to hit one. but chodas says that a water impact might cause little to no damage. “it comes in so quickly that there’s really not a chance for a massive amount of water to be displaced that would cause a tsunami.”
how does this compare with the asteroid that wiped out the dinosaurs?
not even close. that asteroid, called the chicxulub impactor, hit what is now the yucatan peninsula in mexico 66 million years ago. it’s estimated to have been 10 kilometres wide — bigger than mount everest.