Another ‘planet killer’ asteroid discovered: Can such asteroid go unnoticed, reach Earth?

November 7, 2022  14:40

Astronomers have discovered another potential "planet-killer" asteroid that, fortunately, won't pose any threat to Earth for at least a few more centuries, according to a new study led by Carnegie Institution for Science astronomer Scott Sheppard, and published in The Conversation magazine.

The potentially planet-killing new asteroid, 2022 AP7, orbits the Sun once every five years and currently crosses Earth's orbit when Earth is on the other side of the Sun. Eventually, at some point, its motion will become synchronous with the motion of the Earth and the asteroid will pass close enough to the Earth—but this will happen after several centuries.

According to, with a diameter between 1.1 km and 2.3 km, asteroid 2022 AP7 is the largest potentially hazardous asteroid discovered in the last eight years. Note that an asteroid with a diameter of more than 1 km is enough to cause massive destruction on Earth. But it is important that this asteroid has been discovered now, and scientists can already follow its behavior.

It is estimated that scientists have already identified about 95% of the potentially hazardous asteroids, which number less than 1,000. A study by Scott Sheppard and his colleagues says that finding the remaining 5%—about 50 asteroids—will require a huge effort.

Why are some asteroids difficult to detect?

Some asteroids are difficult to detect because they orbit in the sector between the Earth and Venus, so to speak, "hiding" under the sun's rays. To detect celestial bodies in this sector, astronomers must make their observations looking in the direction of the Sun, which is very difficult due to the brightness of the Sun. For example, modern space telescopes such as James Webb and Hubble are never pointed at the Sun because the star's brightness would burn out their sensitive optics. Such asteroids can be detected during twilight hours and twice a day for 10-minute periods.

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That is why astronomers have only a limited understanding of the nature of the asteroids hidden in this region, and sometimes they surprise us by coming too close to Earth. For example, an asteroid called 2021 UA1 passed Earth in 2021—just a few thousand kilometers over Antarctica. On a cosmic scale, this is extremely close range and is considered dangerous. However, the 2021 UA1 was only two meters wide, and therefore did not pose a significant threat.

In 2019, another asteroid—with a diameter of 100 meters—passed at a distance of about 70,000 kilometers from the Earth. It was announced publicly just hours before the asteroid flew by the Earth. Although it wasn't that close to Earth, it was much more worrisome in size.

Moreover, some of these asteroids even reach the Earth. For example, in 2013, a much smaller asteroid—only 20 meters across—suddenly arrived and exploded in the sky over the city of Chelyabinsk in southeastern Russia, shattering the windows of thousands of buildings.

How protected is Earth from such asteroids?

Astronomers, thanks to their observations, fortunately, are able to calculate the trajectories of asteroids for several centuries, and currently there are no such asteroids that should worry mankind. Furthermore, scientists have also long been taking steps to divert Earth-threatening asteroids before they hit Earth.

One such attempt was already made this September when NASA's DART mission successfully changed the trajectory of the 160m-wide asteroid, Dimorphos, orbiting the 780m-wide asteroid Didymos. The success of this first-of-its-kind experiment proves that as long as humanity is able to learn about such dangers at an earlier phase, it can save the planet Earth from such “surprises.”

Near-Earth Object Surveyor.JPG (46 KB)

NASA plans to use the near-Earth object (NEO) Surveyor telescope, which should be launched in 2026, to detect potentially dangerous objects for the Earth at an early stage. It is expected to be able to survey the Solar System very efficiently—including the blind spots caused by sunlight.

NEO Surveyor.JPG (48 KB)

Chinese researchers also recently proposed to deploy a new system consisting of six spacecraft in orbits similar to Venus, to detect and warn of asteroids potentially threatening the Earth as soon as possible.

The CROWN mission is planned to use six wide-angle near-Earth observatories, which will be steered by the main spacecraft. 

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