Planetary Defense: More than 40,000 Near-Earth Asteroids Now Known
For years, the speed of discovery of near-Earth asteroids has been picking up pace. For a few days now, we have known more than 40,000 of them.
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There are now more than 40,000 near-Earth asteroids known, i.e. celestial bodies that come close to Earth's orbit on their paths around the sun – but not necessarily to Earth itself. The European Space Agency ESA has drawn attention to the milestone reached now, which points to its own share in achieving it. According to the latest figures, exactly 877 of these near-Earth asteroids have a diameter of more than one kilometer, another 11,479 are over 140 meters. The vast majority of all these asteroids are therefore smaller and would not cause global destruction if they impacted Earth. Fortunately, none of the 40,000 now known asteroids pose a threat anyway, the ESA assures.
Number is likely to increase much faster soon
Humanity has only known near-Earth asteroids for a relatively short time, the space agency recalls. The first, Eros, was only discovered in 1898. By 1980, a total of 44 had been found, after which their number slowly increased. At the turn of the millennium, we still knew fewer than 1000 near-Earth asteroids, the 10,000 mark was then broken in 2013. Six years later, the 20,000 mark fell, and it only took another three years for the next 10,000. Another three years later, there are now another 10,000 more. In the coming years, the new Vera C. Rubin Observatory in Chile is expected to ensure that the number of known near-Earth asteroids increases significantly faster, the ESA also writes.
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An asteroid is considered near-Earth if it approaches the sun to within 1.3 astronomical units (AU) on its orbit, with the distance between Earth and the sun being exactly one AU. A potentially hazardous asteroid (PHA) approaches Earth's orbit to within 7.5 million kilometers (0.05 AU) and has a diameter of at least 140 meters. We currently know slightly more than 2500 of these. The current figures can be viewed in the freely available database of NASA's Center for Near Earth Object Studies (CNEOS). Approximately one-third of the 40,000 known near-Earth asteroids have a diameter of 30 to 100 meters, which is likely only about two to three percent of all near-Earth asteroids of this size.
(mho)
