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 cruiser Apophis since its discovery in 2004. And for good reason, initial estimates based on its preliminary orbit suggested the asteroid would come dangerously close to our planet in 2029 Recent follow-up scans had also hinted that the object could still hit Earth in 2068. Its size (about 340 meters in diameter) raised fears then. A collision with Earth, however unlikely, could indeed release the equivalent of 1,151 megatons of TNT.
That said, all threats are now averted, 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 action for the past year, the researchers relied on the antennas of the Deep Space Network in California, and on the Green Bank Telescope in West Virginia.
After refining initial observations, astronomers found that there was no real risk of impact in 2029. More good news:the object will not hit neither will Earth in 2068, or in the next hundred years . In fact, the space rock has been removed from NASA's Sentry Impact Risk Table.
" When I started working with asteroids after college, Apophis was the go-to object 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 we may uncover when it [next] approaches in 2029 ” .
In 2029, Apophis will approach about 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. Then the same thing happens with the other side, since the body is rotating. We then observe temperature differences on the surface while each side receives photons, which leads to a modification of the movement of the object. These changes are very small, but they accumulate over time. That is why when one of these objects gets closer, this effect must be considered.
Finally, let's remember that for now, the two most dangerous near-Earth objects for Earth are still 29075 (1950 DA) and the asteroid Bennu. The former has a 1 in 8300 (0.012%) chance of hitting Earth in the year 2880, while Bennu has a 1 in 2700 (0.037%) chance of crashing into us between the years 2175 and 2199.
