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When it returns in 2068, the asteroid Apophis will have virtually no chance of touching Earth.
In fact, the 370-meter (1,210-foot) piece of space rock will pose no danger for at least another century, resulting in its removal from ESA’s Hazard List and Sentinel Impact Hazard Table. from NASA.
“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has dropped from hundreds of kilometers to just a handful of kilometers when projected to 2029,” he said. said astronomer Davide Farnocchia of the Center for Near-Earth Object Studies at NASA.
“This greatly improved knowledge of his position in 2029 gives more certainty about his future motion, so we can now remove Apophis from the risk list.”
Apophis was first discovered in 2004, and early projections suggested that the asteroid had a worrying 2.7% chance of hitting Earth by 2029. Although this was quickly ruled out, Apophis has a close approach to Earth about every eight years; because its orbit was difficult to observe and characterize, the possibility of impact at a later date remained undefined.
Gradually, over the 17 years that astronomers have observed Apophis, his path in space has become clearer.
Last year, the greatest danger was determined to be the close approach of the asteroid in 2068. Farnocchia and his colleague David Tholen measured the Yarkovsky effect – that is, the heating on the Sun side. of the asteroid that generates a small amount of thrust – and found that it generates 170 meters of drift per year.
The other big potential problem affecting the asteroid’s trajectory is the flyby of 2029. According to projections, Apophis will fly over the Earth at a distance of only 38,000 kilometers – about 10 times closer than the Moon. At this proximity, Earth’s gravity will affect the asteroid’s orbit, possibly bringing it closer to a collision course.
With these two influences in mind, astronomers have recalculated Apophis’ path projection. The chance of impact in 2068 remained. It was only one in 150,000, but it’s still a concern, given the damage it could cause.
Now more data has been added to the calculations. The last flyby of the asteroid was just a few weeks ago – on March 6, 2021, Apophis approached within 10 million miles of Earth.
For months before, it was visible in the sky and astronomers watched it closely; then the March 6 flyby allowed scientists to reduce its location to an incredibly precise distance of 150 meters.
In turn, the discovery allowed the projections to be further refined, and we are now officially safe from Apophis for a very long time. Considering the asteroid has been on the Sentinels Risk List and Impact Risk Table since its discovery, this is a great relief.
When Apophis passes in 2029, it will provide scientists with a great opportunity to study its size, shape and speed of rotation, without the threat of disaster also looming. It will be the last such opportunity for quite some time – after 2029, its “close approaches” will become increasingly distant.
“When I started working with asteroids after college, Apophis was the go-to kid for dangerous asteroids,” Farnocchia said.
“There is a certain sense of satisfaction to see it taken off the risk list, and we look forward to the science we may uncover as it nears closure in 2029.”
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