Source: Tadpole Pentagram
Image description: In February 2013, a small celestial body the size of a semi-trailer exploded in the sky above the Russian city of Chelyabinsk.In the vast universe, Earth is not an isolated island, often visited by visitors from the depths of the solar system - asteroids, quietly approaching our home.
On October 24th (Thursday), four 'massive' small asteroids arrived at their respective perihelion points one after another in an unprecedented 'space gathering' within 12 hours. Although these asteroids, known as 'potential threats' of space rocks, may sound a bit tense, fortunately, they pose no threat to life on Earth.
Intimate contact with space rocks
The main characters of this 'space gathering' include four differently sized asteroids, the smallest of which is about 30 meters wide, while the largest is about 177 meters wide, roughly equivalent to the height of a building nearly 60 stories tall.
The first to arrive was the asteroid 2015 HM1, with a width of about 30 meters, estimated to reach perihelion at 12:36 pm Beijing time on October 24th, at a distance of about 5.5 million kilometers, equivalent to 14 times the average distance between the Earth and the Moon. Next came the asteroid 2024 TP17, with a width of about 52 meters, reaching perihelion at 16:20 on the 24th, at a distance of about 4.7 million kilometers.
The highlight is a pair of 'twins' that appeared almost simultaneously - the asteroids 2002 NV16 and 2024 TR6, arrived at the perigee at 23:47 and 23:51 on the 24th of October Beijing time, respectively. Among them, 2002 NV16 is the largest of the four asteroids, with a width of about 177 meters, and the closest distance to Earth is about 4.5 million kilometers. The 2024 TR6, with a width of about 46 meters, follows closely, with the closest distance to Earth being about 5.6 million kilometers.
It is worth noting that two of these four asteroids - 2024 TR6 and 2024 TP17 - were only discovered this month. 2024 TR6 was first observed on October 7th, while 2024 TP17 made its appearance on October 12th. Such discoveries are not uncommon. According to the Catalina Sky Survey project statistics, astronomers discover about 2,000 near-Earth asteroids each year, with most of them being identified when they are close to Earth.
Caption: The positions of tens of thousands of near-Earth asteroids around Earth (NASA image)
Impact of asteroid collisions
If an asteroid is considered a 'potential threat,' it must meet two criteria: first, its Minimum Orbit Intersection Distance (MOID) with Earth must reach or be less than 0.05 AU, which is 7.48 million kilometers (where 1 AU represents an astronomical unit, the average distance from Earth to the Sun, approximately 0.15 billion kilometers); second, its absolute magnitude is not higher than 22. For asteroids, absolute magnitude is an important indicator of size measured by brightness. A smaller absolute magnitude value indicates a larger celestial body. For example, an asteroid with an absolute magnitude of 22 may have a diameter between 110 and 240 meters, while an asteroid with an absolute magnitude of 21.5 may range in diameter from 130 to 300 meters.
Fortunately, the four 'potential threat' asteroids visiting Earth currently do not have the possibility of impacting Earth. However, if an asteroid were to impact Earth, it would have a significant impact in various ways, not just the damage caused by a direct impact on the ground. These effects also include earthquakes, tsunamis, drastic changes in the atmospheric environment, forest fires triggered by impacts, and the severity of these effects is closely related to the size of the asteroid.
For those smaller asteroids, they may disappear completely due to intense friction and burning in the atmosphere before reaching the Earth's surface. An asteroid the size of a football field (approximately hundreds of meters) is enough to bring catastrophic consequences to a specific local area on Earth. If an asteroid has a diameter of several thousand kilometers, equivalent to the size of a town, it would cause a global catastrophe, possibly leading to mass extinctions. For example, it is speculated that the extinction of dinosaurs was caused by a catastrophic event 65 million years ago when an asteroid with a diameter of 10 kilometers hit Earth.
So far, astronomers have mapped the orbits of over 33,000 near-Earth asteroids. For at least the next 100 years, none of these asteroids will pose an impact risk to Earth, providing ample time for humanity to gradually strengthen its own response capabilities. At this stage, the most critical task is to early detect potentially threatening asteroids and accurately assess the risks they may bring. (Compiled by: Liu Yun)
Reference Information
https://
https://
Planners: Liu Kun, Li Peiyuan, Zhang Chao, Yang Liu
Reviewers: Research Curator at Peking Observatory, Li Xin