A 68-meter Diameter Asteroid Approaches Earth Undetected by Scientists.
2021 SG, an asteroid measuring between 42 to 94 meters in width, with an average diameter comparable to the wingspan of a Boeing 747, passed close to Earth on September 17 (Hanoi time), according to the International Astronomical Union’s (IAU) Minor Planet Center. However, scientists were unable to see this asteroid approaching and only detected it the following day. The reason is that it approached from a “blind spot” – the direction of the Sun.
Illustration of an asteroid approaching Earth. (Image: PIXABAY).
Most asteroids detected by astronomers approach Earth from the “front,” meaning they come from outside the solar system, getting closer to both Earth and the Sun at the center. However, there are also asteroids that come from “behind,” meaning they approach Earth from the Sun’s direction and then move outward from the solar system.
It is very difficult to see these celestial bodies as they near our planet, especially since they often approach during the day when visibility is limited due to the Sun’s bright light. Generally, the best time to detect them is during twilight. This is also true for any celestial bodies located in the space between Earth and the Sun, such as Mercury and Venus.
2021 SG passed very close to Earth, at only half the distance between Earth and the Moon. It was nearest to our planet around 3:28 AM, flying over Greenland and Canada. This is a very close distance, as most asteroids that pass by Earth are much farther away.
With a large size and a speed of over 85,000 km/h, 2021 SG would cause significant damage if it were to collide with Earth.
Previously, a smaller asteroid caused severe consequences when it struck Earth on February 15, 2013. The 17-meter-wide asteroid exploded over Chelyabinsk, Russia. The shockwave from the explosion shattered windows in six cities and required medical attention for 1,500 people.
Astronomers with telescopes and advanced technologies can detect, catalog, and track a large number of objects in space, including small debris from old satellites in orbit. However, they currently do not have a superior method to monitor objects approaching Earth from the direction of the Sun.
To improve this situation, NASA is developing a new space telescope named Near-Earth Object (NEO) Surveyor. This telescope is expected to launch in 2026 and will operate in the space between Earth and the Sun, helping scientists observe celestial bodies more effectively.
