Civilization-threatening asteroids could be hiding in Sun’s glare

On February 15, 2013, a massive meteor, about the size of a semitrailer, zoomed in from the direction of the rising sun and burst into a fiery explosion above the city of Chelyabinsk, Russia. For a hot minute, that meteor lit up even more than the sun and blew up with a force 30 times bigger than the bomb that wrecked Hiroshima. It happened about 14 miles up in the sky. The blast wrecked windows in over 7,000 buildings, left folks on the streets temporarily blind, gave instant UV burns, and hurt more than 1,600 people.

The Chelyabinsk meteor is believed to be the largest space object to dive into Earth’s atmosphere in over a century. But get this – not a single observatory on Earth caught a glimpse of it before the grand entrance. Sneaking in from the sun’s direction, that rock stayed under the radar in our major blind spot until it was game over.

Luckily, stuff like this doesn’t happen all that often. Rocks the size of the Chelyabinsk meteor – about 66 feet (20 meters) wide – only break into Earth’s atmosphere every 50 to 100 years, says the European Space Agency (ESA). Bigger asteroids hit even less frequently. So far, astronomers have tracked over 33,000 near-Earth asteroids and figured out that none of them are a threat to smack into our planet for at least the next hundred years.

Knowing the existence of hazardous asteroids is paramount

Yet, here’s the kicker – you can’t figure out the danger of an asteroid you can’t spot. And guess what? There are tons of them out there, some big enough to wipe out cities and maybe even cause mass-extinction scenarios, all cruising around our star on paths we can’t predict, say the experts talking to Live Science. It’s a tough reality that’s got astronomers both worried about what might go down and fired up to uncover as many hidden asteroids in our solar system as possible. Once we know about them, we can keep an eye on the deadly ones and push them off course if needed. And if all else fails, we can at least give folks a heads-up to move away and dodge the disaster.

Right now, the sun’s playing hide-and-seek with a bunch of asteroids. There’s a crew of Apollo asteroids always doing a spin, hanging out mostly way past Earth’s orbit but deciding to swing by and get closer to the sun every now and then. Then there’s the mysterious Atens, a group of asteroids that do their rounds mostly inside Earth’s orbit, always sticking to the sunny side of the planet.

“Aten asteroids are the most dangerous, because they cross Earth’s orbit just barely at their most distant point,” Scott Sheppard, a staff scientist at the Carnegie Institution for Science, told Live Science. “You would never see one coming, to some degree, because they’re never in the darkness of the night sky.”

Just like any asteroids, most of these sneaky space rocks are probably small enough to sizzle away in Earth’s atmosphere if they come in contact. However, there’s a catch – there are likely plenty of undiscovered asteroids out there that are over 460 feet (140 m) in size. They’re big enough to make it through the atmosphere in one piece and wreak havoc with some serious local damage upon impact. These potentially devastating asteroids are sometimes called “city killers.”

The Sun’s glare might be preventing asteroids from detection

And here’s the wild part – there might be way bigger things out there hiding in the sun’s brightness. It’s super uncommon, but there could be a couple of “planet killer” asteroids, each over 3,280 feet (1 km) in size, playing hide-and-seek. These mammoths have the power to toss up so much dust that it could set off a global extinction event, Sheppard mentioned.

Back in 2022, Sheppard and his buddies stumbled upon a planet killer that was playing hide-and-seek with the sun. They spilled the details in a paper in The Astronomical Journal. These researchers were on the prowl for asteroids hanging out near Venus. They snagged time on a bunch of big telescopes, scanning the skies for five to ten minutes every night at twilight. Lo and behold, they found 2022 AP7 – a colossal space giant stretching a mile wide (1.5 km) with a weirdo five-year orbit that practically keeps it invisible to telescopes most of the time.

Right now, 2022 AP7 only crosses paths with Earth’s orbit when we and the asteroid are on opposite sides of the sun, so no worries. But here’s the kicker – over thousands of years, that gap is gonna shrink, inching the two things closer and closer to a potentially disastrous crash. And bet on it, there’s probably more where that came from.

Up there, hundreds of miles above Earth and even farther out, space telescopes don’t have to deal with Earth’s atmosphere messing things up. That’s a game-changer because it gives them a killer move: infrared imaging. This means they can pick up on the heat given off by space stuff, not just rely on the sunlight bouncing off them like regular telescopes do.

NEOWISE may not be enough to detect all asteroids

Right now, there’s just one infrared space telescope on the hunt for near-Earth asteroids, and it goes by the name of the Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE. Back in 2009, it started its journey as WISE, meant for spotting stuff way out there. But then, in 2013, after the Chelyabinsk drama, WISE woke up from a two-year nap, transformed into NEOWISE with fresh software and a new mission: spotting those potentially problematic near-Earth asteroids.

However, NEOWISE could never check out the sun’s side, and Mainzer predicts its mission will wrap up for good by July 2024. After that, it’s up to the surveys done from the ground to spot new asteroids until the next batch of space telescopes is up and running later in the decade.

Good news – there are two upcoming spacecraft that are set to shed some light on the mysteries of the solar blind zone: NASA’s NEO Surveyor, scheduled to take off in 2027, and ESA’s NEOMIR, still in the early planning stages and aiming for a launch no earlier than 2030, according to Conversi.