An asteroid passed by Earth just 3,000 kilometers from the planet’s surface last week, but it went unnoticed until after the fact, NASA data showed.
Dubbed 2021 UA1, the asteroid, which skimmed by Antarctica last Sunday, was much smaller—just 2 meters in diameter, which is roughly the size of a golf cart. As such, it is unlikely that there would actually have been any damage if it impacted the planet, as it would likely have burned up in the atmosphere.
But while the damage it would have caused should have been minimal, the real danger is that an asteroid came so close to the planet and nobody noticed until after the fact.
2021 UA1 flew very close to the planet, and is estimated to be the third closest asteroid flyby ever recorded without impact, after 2020 QG in August 2020 and 2020 VT4 in November 2020.
With a distance of just 3,000 kilometers, 2021 UA1 was closer to Earth than the Moon, which orbits the planet at a distance of 384,400 kilometers. A simulation shows how close it was.
— Tony Dunn (@tony873004) October 27, 2021
2021 UA1 is not as close to Earth as the International Space Station, which has an average altitude of 408 kilometers. However, it is much closer to the planet than many of Earth’s communication satellites, most of which orbit at a distance of about 35,785 kilometres.
Asteroid impact is one of the biggest potential disasters that can affect the planet, which is why space agencies around the world monitor many of these asteroids, calculate their sizes, distances, orbits. and whether they could potentially attack the planet.
So why didn’t scientists detect 2021 UA1 before passing by the planet?
This is because it came from a blind spot.
Most asteroids discovered by agencies such as NASA come from the “front” of Earth, which means they come from the direction that the interior of the Solar System faces toward Earth and the Sun.
But there are asteroids that come from “behind”, which move from the Sun’s direction toward Earth and outward.
These objects are therefore very difficult to see as they approach Earth, especially as they often arrive during the day when visibility is low due to the glare of the Sun.
Generally, the best time to view these objects is during twilight. This is the case for all objects in the space between Earth and the Sun, such as the planets Mercury and Venus.
In a picture an asteroid is seen moving towards Earth. (credit: Pixabay)
This isn’t the first time such an asteroid has passed the planet without anyone noticing it: on September 16, 2021, SG, an asteroid with diameters of 42 and 94 meters, approached the planet about half the distance between Earth and the Moon. Passed by, and no one noticed until a day later.
With its large size and speed of 85,748 km/h (about 23.8 km/s), the asteroid certainly could have had an impact if hit.
The last known significant asteroid impact occurred on February 15, 2013, when an asteroid exploded in the air over Chelyabinsk, Russia. The asteroid was 17 meters wide, and resulted in no casualties, the shock wave from the explosion broke windows in six different Russian cities and caused 1,500 people to need medical attention.
This asteroid also came from “behind”.
The destructive nature of asteroids, even small ones, is somewhat well known to experts, with space agencies around the world monitoring potentially catastrophic impacts as well as possible means of preventing them. doing research.
One way to potentially prevent an asteroid impact is through the use of deflection, which would mean launching something to slightly change an asteroid’s path. Chief among these efforts is the Double Asteroid Redirection Test (DART) mission, to be launched in November, the result of efforts by NASA and the Applied Physics Laboratory.
In layman’s terms, this means punching the asteroid with a rocket with enough speed to change its direction by a fraction of a percent.
However, this method has its drawbacks, especially timing. It took a long time and resource to develop and launch the spacecraft used in the Dart mission. In the case of an asteroid impact that seems so sudden, that kind of timing could be a luxury the planet cannot afford.
This is especially true with asteroids coming from “behind”, as they are far more difficult to track.
In fact, NASA currently has no means of accurately detecting asteroids close to the Sun.
However, that may soon change. NASA is in the midst of building a new space telescope that will help with this effort. Called the Near-Earth Object (NEO) Surveyor Space Telescope, it is to be launched in 2026 and will be in orbit between Earth and the Sun, allowing it to better detect these objects. It is hoped that the NEO surveyor will help find about 90% of near-Earth asteroids with a width of 140 meters or more – a size that could destroy a city if impacted.
Back in March, NASA announced that the planet was at no risk of an asteroid impact for the next century, after astronomers calculated that 9942 Apophis – a massive 340-meter asteroid – would safely pass the planet at a distance. Under 32,000 km. On 13 April 2029.
However, as events such as the near flyby of 2021 UA1 show, the risk of unexpected asteroids close to the Sun remains a potential threat.