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at 00:39 on september 5, 2024, beijing time, an asteroid entered the earth's atmosphere and disintegrated and exploded at an altitude of about 25 kilometers northeast of the philippines. before the asteroid entered, astronomers discovered it and accurately predicted the time and location of its impact on the earth. so far, the number of asteroid impacts that humans have successfully warned has increased to 9. at the same time, this is also the first time that my country's monitoring network has carried out relay tracking observations on a warning asteroid.

at 13:43:41 on september 4, the asteroid was first discovered by the 1.5-meter telescope of the catalina sky survey (css). the target was then submitted to the international astronomical center's near-earth asteroid confirmation page with the temporary name caqtdl2, and its probability of impacting the earth was calculated to be over 30%. subsequently, multiple observatories in the united states, chile, and australia conducted follow-up observations, and the purple mountain observatory of the chinese academy of sciences also tracked it using telescopes at overseas sites.

at 20:00 on the same day, the xuyi observatory of the purple mountain observatory of the chinese academy of sciences had the conditions for observation. the near-earth object telescope immediately started tracking observations, closely monitoring the motion trajectory of the asteroid. at the same time, the telescope located at the ali station in tibet was started to carry out relay observations, and ephemeris guidance for radar observations was provided to relevant domestic units.

at 21:55, the international astronomical center numbered the asteroid 2024 rw1 and predicted that the asteroid would hit the northern philippines at 00:39 beijing time on 2024/9/5. in the end, the asteroid entered the earth's atmosphere at a speed of about 20 kilometers per second as expected, disintegrated and exploded at an altitude of about 25 kilometers from the ground, and did not cause a major impact on the lives of local people. the predicted impact time and location were relatively accurate.

xu zhijian, assistant engineer at the purple mountain observatory of the chinese academy of sciences, told modern express that when the asteroid was first discovered, its brightness was only 21 magnitude, its estimated diameter was only 1-2 meters, and its absolute magnitude was 32.19, which was very dim. as it gradually approached the earth, it became brighter and brighter. according to observations by my country's observation equipment, the asteroid's brightest brightness reached about 15 magnitude.

the impact of outer space objects is a major potential threat faced by all mankind in the world. every year, there are more than 4,000 near-earth asteroid impacts with a diameter of less than 10 meters. on february 15, 2013, the chelyabinsk asteroid impact in russia caused large-scale damage to houses and casualties.

after the chelyabinsk incident, the international asteroid warning network (iawn) was established to strengthen international cooperation and data sharing in the field of near-earth object observations and jointly respond to the threat of near-earth object impacts. before 2024 rw1, eight asteroids had been discovered before they hit the earth.

xu zhijian introduced that chinese astronomers have conducted network observations of some known near-earth asteroids. unlike in the past, this is the first time that my country's monitoring network has achieved relay tracking observations of early-warning asteroids, marking an important progress in my country's asteroid defense work.

in february 2018, my country joined the iawn network as a formal member. the 1.04-meter near-earth object telescope at the xuyi observatory of the purple mountain observatory is currently the backbone equipment for my country to contribute shared data, and has been continuously carrying out near-earth asteroid monitoring and early warning work. so far, 41 near-earth asteroids have been discovered.

modern express/modern+ reporter li ming/text

(photo courtesy of purple mountain observatory, chinese academy of sciences)