In 2029, a large asteroid will whizz past Earth so close it’ll be visible to the naked eye, but thankfully models of its orbit rule out an impact in the next century. But could collisions with other asteroids bounce it off-course into us? To find out, astronomers have now crunched the paths of 1.3 million known asteroids.
In 2004, astronomers discovered an asteroid designated 99942 Apophis, which quickly raised some eyebrows. Initial observations suggested it had a 2.7% chance of impacting Earth on April 13, 2029, and since its large diameter of up to 370 m (1,210 ft) could cause widespread destruction if it hit, Apophis was given a rating of 4 on the Torino scale of impact hazards – the highest rating ever recorded. Thankfully, further observations quickly ruled out a collision on that day, as well as during other close passes in 2036 and 2068.
That said, the 2029 event is still a pretty close shave – Apophis will zip past at about 37,000 km (23,000 miles), or potentially as close as 32,000 km (20,000 miles). That’s less than one 10th the distance to the Moon, and the latter is even closer than geostationary satellites. It’s so close that with dark enough skies the rock will actually be visible to the naked eye. A small nudge, say from another asteroid, might be the difference between a city being wiped off the map or not.
“Given how closely Apophis will pass Earth, there is a possible risk that a deflection from its current trajectory may move Apophis closer to impacting us,” said Benjamin Hyatt, co-author of the study. “Hypothetically, another asteroid colliding with Apophis could cause such a deflection, motivating us to study this scenario however unlikely it may be.”
So, researchers from Western University and the University of Waterloo calculated the paths of all 1.3 million known asteroids in the solar system, to see if Apophis might be involved in a cosmic game of billiards before its appointment with Earth. Thankfully, all direct collisions were ruled out, but it’s not without a few close calls of its own.
In December 2026, for instance, Apophis will swing within 10,000 km (6,200 mi) of a huge asteroid called Xanthus, measuring 1.3-km (0.8-mi) wide. The two rocks will miss each other by just four hours, although the team says there is a chance that Apophis could be struck by some small, loose debris from Xanthus. Thankfully though, that shouldn’t change its trajectory.
Although there are no known impact threats to Earth in the next century, it pays to keep watching the skies. If we do spot something on a collision course far enough in advance, the recent DART mission has shown we could use a bit of billiards ourselves to knock it off-course.
“Asteroid Apophis has fascinated us as a species since its discovery in 2004: it was the first credible threat from an asteroid to our planet,” said Paul Wiegert, co-author. Of the study. “Even now that we know it’s on course to miss us by a safe margin, astronomers remain vigilant. It’s the asteroid we just can’t stop watching.”
The research was published in the Planetary Science Journal. Some of Apophis' closest encounters are modeled in the video below.
Source: Western University
