we are quiet for at least 100 years

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The list of objects posing a potential threat to Earth is quite short, and for a time the asteroid Apophis was one of them. But not anymore. The object has indeed just lost its “potentially dangerous” status for at least the next 100 years, according to new observations.

Astronomers have been monitoring the near-Earth device Apophis since its discovery in 2004. And for good reason, initial estimates based on its preliminary orbit suggested that the asteroid would approach dangerously close to our planet in 2029. Recent tracking analyzes had also suggested that the object could still strike the Earth in 2068. Its size (about 340 meters in diameter) gave rise to fears. A collision with Earth, as improbable as it is, could indeed release the equivalent of 1,151 megatons of TNT.

A little respite

That said, all threats are now over, at least for a while. A team of astronomers took advantage of the passage of the asteroid near the Earth on March 5 (at 0.11 astronomical units) to adjust the calculations of its trajectory.

With the radar telescope at the Arecibo Observatory in Puerto Rico being out of play since last year, the researchers relied on the antennas of the Deep Space Network in California, and the Green Bank telescope in West Virginia.

After refining the initial observations, astronomers found that there was no real risk of impact in 2029. Another good news: the object will not hit Earth in 2068 either, nor in the next hundred years. In fact, the space rock has been removed from the Sentinel impact risk table from NASA.

“When I started working with asteroids after university, Apophis was the benchmark for dangerous asteroids”said Davide Farnocchia, who analyzes asteroid orbits for NASA. “There is a certain sense of satisfaction to see it removed from the risk list, and we look forward to the science that we may discover when it is released. [prochaine] approaching in 2029 ”.

Radar images of the asteroid Apophis on March 8, 9 and 10 as it passed within 17 million kilometers of Earth. Credits: NASA / JPL-Caltech and NSF / AUI / GBO

Yarkovsky effect

In 2029, Apophis will approach approximately 32,000 kilometers from the surface of our planet. On this occasion, astronomers will be able to analyze its “Yarkovsky effect”.

During a revolution around the Sun, one side of an asteroid receives more light (photons) than the other. The same thing then happens with the other side, since the body is rotating. One then observes temperature differences on the surface while each side receives photons, which causes a modification of the movement of the object. These changes are very small, but they accumulate over time. Therefore, when one of these objects gets closer, this effect must be considered.

Finally, remember that for the time being, the two near-Earth objects most dangerous for Earth are still 29,075 (1950 DA) and the asteroid Bennu. The former has a 1 in 8,300 (0.012%) chance of hitting Earth in 2880, while Bennu has a 1 in 2700 (0.037%) chance of hitting us between the years 2175 and 2199.





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