The Chelyabinsk meteor is considered the largest natural space object to enter the Earth’s atmosphere in more than 100 years. But no observatory on Earth noticed this. The stone coming from the direction of the sun remained hidden in our biggest blind spot until it was too late.

Fortunately, such events are rare. According to estimates by the European Space Agency (ESA), rocks the size of the Chelyabinsk meteorite (about 20 meters) breach the Earth’s atmosphere every 50 to 100 years. Larger asteroids fall even less frequently. To date, astronomers have mapped the orbits of more than 33,000 near-Earth asteroids and found that none of them are at risk of hitting our planet for at least the next century.

But you can’t calculate the risk of an asteroid you can’t see — including some massive enough to destroy cities and potentially trigger a mass extinction — moving in mysterious orbits around our star, experts told Live. Science. This stark reality has led astronomers to worry about the possible consequences and to seek out as many of the hidden asteroids in our solar system as possible. Once we know about them, deadly asteroids can be observed and diverted if necessary, or if all else fails, the population can be warned to relocate to avoid mass casualties.

“The most problematic object is the one you don’t know about,” Amy Meinzer, a professor of planetary science at the University of Arizona and principal investigator of two NASA asteroid-finding missions, told LiveScience. “If we know what’s out there, we can do a much better job of assessing the real risk.”

The Sun hides countless asteroids at all times. These include the Apollo group of orbiting asteroids (near-Earth objects that spend most of their time well beyond Earth’s orbit but occasionally approach the Sun by crossing our planet’s path) and a mysterious class of almost completely rotating asteroids called Atens. Inside the Earth, always on the day side of the planet.

“Atene asteroids are the most dangerous because they can barely cross Earth’s orbit at its farthest points,” Scott Sheppard, a research associate at the Carnegie Institution for Science, told LiveScience. “You never see them coming because they’re never in the dark of the night sky.”

As with all asteroids, most of these hidden space rocks are small enough to burn up completely in Earth’s atmosphere upon contact. But Meinzer estimates that there are also many undiscovered asteroids larger than 460 feet (140 m) in diameter that are large enough to survive falling into the atmosphere and cause devastating local damage upon impact. Asteroids with such destructive potential are sometimes called “city killers.”

“We think we found about 40% of these asteroids in the 140-meter region,” Meinzer said. According to NASA estimates, approximately 14,000 individuals are expected to be present.

Much larger objects may await us in sunlight. A few “planet-killer” asteroids larger than 3,280 feet (1 km) in diameter and capable of kicking up enough dust to trigger a global extinction event may be lurking in sunlight, although they are extremely rare, Sheppard said.

In 2022, Sheppard and his colleagues discovered one such killer planet hidden by the sun, which they described in a paper in The Astronomical Journal. Researchers were looking for asteroids near Venus and borrowed time from several large telescopes to scan the horizon for five to ten minutes at dusk each evening and discovered 2022 AP7, a mile-wide (1.5 km) giant with an odd age of five years. . The orbit that made the giant space rock almost permanently invisible to telescopes.

“When it’s in the night sky, it’s farthest from the sun and very faint,” Sheppard said. “The only time it’s even remotely bright is when it’s inside the Earth, close to the Sun.”

Currently, 2022 AP7 only passes Earth’s orbit when our planet and the asteroid are on opposite sides of the Sun, making it harmless. But this gap will gradually shrink over thousands of years, bringing the two objects closer to a potentially devastating collision. And probably not the only one.

“Through our research to date, we have found that there may be more Aten asteroids, probably several kilometers wide,” Sheppard said. he added. Source