'Planet Killer': Asteroid hiding in sunlight may one day collide with Earth

Astronomers have discovered a giant asteroid hiding in the sunlight. They dubbed it the "planet killer" because the consequences of its collision with the planet will affect several continents. And it is possible that one day it may collide with the Earth.

As Space.com tells us, the asteroid, named 2022 AP7, has a diameter of 1.5 km: it is the largest potentially dangerous asteroid detected in the last 8 years.

Why are such asteroids hard to detect?

The asteroid has avoided detection for so long because it orbits in an area between Earth and Venus. To detect space objects in this area, astronomers must look in the direction of the sun, which is notoriously difficult because of the brightness of that star. Even flagship telescopes, including the James Webb and Hubble telescopes, never look toward the sun because the brightness of the star would damage their sensitive optics.

It is for this reason that astronomers have only a limited understanding of the nature of the asteroids lurking in this region, and sometimes there are surprises. For example, in 2013, a much smaller asteroid - with a diameter of only about 20 meters - suddenly fell from the direction of the Sun and exploded over the city of Chelyabinsk in southeastern Russia, blowing out windows in thousands of buildings.

"Only about 25 asteroids with orbits completely within Earth’s orbit have been discovered to date because of the difficulty of observing near the glare of the Sun," said astronomer Scott S. Sheppard, who is also the lead author of the paper describing the new discovery.

Are there many such unknown asteroids?

2022 AP7 would do more damage if it hit Earth than the asteroid that fell on Chelyabinsk. Its detection was made possible by the ultra-sensitive Dark Energy Camera (DEC) at the Cerro Tololo Observatory in Chile, which scans the sky during the twilight hours. It is during these hours that these asteroids can be seen twice a day for 10 minutes.

"So far we have found two large near-Earth asteroids that are about 1 kilometre across, a size that we call planet killers," Sheppard said.

Because the inner asteroids of the solar system are so difficult to detect, they are underrepresented in models of the total number of asteroids in the solar system. However, Sheppard believes that there are only a few unknown "killer planets" left in this hard-to-see region.

The good news, he says, is that many of these unknown asteroids are probably moving in orbits that keep them at a safe distance from Earth.

"There are likely only a few NEAs with similar sizes left to find, and these large undiscovered asteroids likely have orbits that keep them interior to the orbits of Earth and Venus most of the time," Sheppard said.

Two more space objects

In addition to the potentially Earth-threatening 2022 AP7, astronomers discovered two other, smaller objects during DEC observations. One is the closest object to the Sun that astronomers have ever seen. Because of its proximity to the star at the center of the solar system, this asteroid, named 2021 PH27, is experiencing the largest general relativity effect of any object in the solar system.

According to Albert Einstein's General Theory of Relativity, massive objects distort space, which can affect the motion of other objects nearby. These very minor effects can be seen as irregularities in the orbits of planets and asteroids, which cannot be explained by the laws of Newtonian physics. Fortunately, both 2021 PH27 and the third asteroid, named 2021 LJ4, move in orbits that do not intersect with Earth's orbit.

More than 2,200 potentially dangerous asteroids under the magnifying glass

Astronomers are currently observing more than 2,200 potentially dangerous asteroids orbiting Earth at dangerously close distances and with diameters greater than 1 km. Such asteroids are of great concern to scientists because if they collide with Earth, they will cause widespread destruction that could affect the entire planet. However, even much smaller asteroids will cause serious problems if they hit densely populated areas. For example, an asteroid as small as 50 meters wide could cause major damage to all of London if it explodes in the sky above the city center.

Fortunately, astronomers have been able to calculate asteroid trajectories centuries in advance, and there are currently no such asteroids to worry us. And before such an asteroid appears, the international space community is hoping for tools to protect the planet.

Such attempts are already underway: in September, NASA's DART mission successfully altered the trajectory of the 160-m diameter asteroid Dimorphos, orbiting the 780-m wide Didymos. The success of this first-of-its-kind experiment proves that if humanity can learn about dangerous asteroids in advance, it can protect the planet from collision.