Near-Earth Object Telescope at Purple Mountain Observatory captures 2024YR4 on Jan 7, 2025. The small bright spot pointed to by the red arrow is the asteroid. (Photo provided to chinadaily.com.cn)
Since early January, Chinese scientists have been continuously observing an asteroid that has a small chance of colliding with Earth in 2032.
By combining global data, astronomers have updated the probability of impact to around 1.5 percent.
"As observational data accumulates, the calculations of its orbit will become more accurate, and the probability of it hitting Earth will also change. So the public need not panic and should await further results from astronomers," said Zhao Haibin, director of and researcher at the Department of Planetary Sciences and Deep Space Exploration at the Purple Mountain Observatory of the Chinese Academy of Sciences.
The asteroid, named 2024 YR4, has an estimated diameter of between 40 and 90 meters, roughly the size of a large building. It was discovered on Dec 27 by an Asteroid Terrestrial-impact Last Alert System telescope in Chile, according to scientists.
On Wednesday, the near-Earth object monitoring system of the United States space agency NASA revised the probability of 2024 YR4 hitting Earth to 1.5 percent, down from its Tuesday estimation of 3.1 percent.
On Tuesday, the European Space Agency's Near-Earth Object Coordination Centre revised its estimation of the probability to 2.8 percent from the previous 2.4 percent.
"The orbit of an asteroid is primarily calculated through optical observations," Zhao said. "Asteroids shine by reflecting sunlight, and observing them with telescopes, along with the surrounding stars in their field of view, helps us determine their coordinates in the celestial sphere. This, in turn, allows us to calculate their orbits."
The orbit of this asteroid has a relatively high eccentricity, meaning that its path is elliptical. It passes near Earth's orbit approximately every four years. The period from the end of last year to the beginning of this year was a good observation window, and there will be another favorable observation window in 2028, he said.
Experts studying asteroids at the CAS indicated that although current technology makes it difficult to directly intercept an asteroid, its trajectory can be altered by a few millimeters per second.
There are several ways to prevent a near-Earth asteroid from colliding with the planet, such as launching rockets to push it off its original path or evacuating people when it is about to collide with the planet, minimizing the effect of impact.
"An asteroid with a diameter of a few dozen meters could devastate an area of several thousand square kilometers, equivalent to a large city, if it hits Earth without any preventive measures," said a scientist who asked to remain anonymous.
Zhao, the researcher, said, "Given that we have already discovered the asteroid, with a diameter of around 50 meters, we will undoubtedly develop a response plan, meaning that the public need not worry excessively."
The International Asteroid Warning Network and the Space Mission Planning Advisory Group have been operating since 2013, monitoring and issuing warnings for asteroids that pose a potential risk of impact.
For an asteroid with a diameter greater than 10 meters and an impact probability of more than 1 percent, the IAWN will issue a warning, calling on astronomers worldwide to monitor it, Zhao said.
"If the asteroid has a diameter greater than 20 meters and a 10 percent probability of impact within the next 20 years, the SMPAG will activate a response mechanism. This involves accurately assessing the impact risk corridor for Earth and preparing civil defense measures," he said.
"If the asteroid's diameter exceeds 50 meters and there is a 1 percent probability of impact within 50 years, active defense plans, such as launching spacecraft to alter its orbit, may be initiated," he added.
At a conference in Beijing in 2018, Chinese scientists discussed the key technologies related to asteroid monitoring and early warning, safety defense and resource utilization.
"If we need to defend against an asteroid with a diameter of around 50 meters, we might need to start deploying measures three to four years in advance," said the scientist who requested anonymity.
Chinese scientists have achieved notable progress in the detection and monitoring of near-Earth asteroids. In particular, the Near-Earth Object Telescope at the Purple Mountain Observatory and the Wide Field Survey Telescope, a collaboration between the University of Science and Technology of China and the Purple Mountain Observatory, have delivered significant results in recent years. To date, China has discovered more than 60 near-Earth asteroids.
"This also reflects China's active commitment to fulfilling its responsibilities as a major nation in the field of asteroid monitoring, early warning and defense," said Zhao.
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