If you get to 2068 you might see the impact of the asteroid Apophis against the Earth

Only a small handful of objects are known to pose a serious threat to Earth, and the giant asteroid Apophis is one of them. Scientists are re-evaluating its potential to hit our planet in 48 years thanks to new observations of the annoying asteroid.

Observations made earlier this year by the Subaru telescope in Hawaii shed light on how the Yarkovsky effect is affecting the orbital path of asteroid 99942 Apophis. This effect is like an integrated propulsion system for asteroids, in which small amounts of radiation entering the object can alter its momentum in space, causing it to deviate slightly from the path gravity would otherwise have chosen. .

“If you don’t take into account the Yarkovsky drift, Apophis is still a threatening object, but not in 2068,” said Dave Tholen, a researcher at the University of Hawaii’s Institute of Astronomy and co-author of the study. “Considering Yarkovsky, the impact scenario in 2068 is at stake. It’s small, but different from zero.”

Tholen, along with Davide Farnocchia of NASA’s Jet Propulsion Laboratory, analyzed the new numbers and found that the Yarkovsky acceleration keeps the Apophis threat by the 2068 window. Their results are presented in new research discussed at the 2020 meeting. virtual of Division of Planetary Sciences of the American Astronomical Society.

Apophis holds the title of third the highest threat in Sentinel risk table from NASA. The Palermo Technical Impact Risk Scale estimate suggests that there is a one in 150,000 chance that Apophis will hit Earth on April 12, 2068 (mark the date on the calendar). Or, if you prefer it as a percentage, there is a 0.00067% probability of impact with Earth. Tholen said the odds are rather 1 in 530,000, a figure used by the NEODyS impact monitoring service which includes a nominal Yarkovsky drift rate. But Tholen said we will have to “be careful with this calculation” as there are other variables to consider. Indeed, we should expect the odds to change over time as astronomers better manage this asteroid’s itinerary.

A collision with Earth, however unlikely it may seem, would be very serious. Apophis, full of nickel and iron, is more than 300 meters wide, which is more than three football fields. A surface impact would release the equivalent of 1,151 megatons of TNT. Such a calamitous event occurs on Earth once every 80,000 years.

So it’s understandable that scientists are keeping an eye on Apophis to improve their estimates. When the asteroid was discovered in 2004, astronomers initially they assigned a horrible 2.7% chance of impact with Earth by 2029. Since then, astronomers have done so discarded this possibility, together with a possible impact in 2036. As for the date of 2068, it cannot be ruled out, at least not yet, as the Yarkovsky effect affects Apophis.

Asteroids, which are exposed to the sun’s rays, absorb a lot of energy. However, over time, this excess heat is redirected into space, but not perfectly evenly through the body of the asteroid. This results in additional acceleration, which can change the trajectory of the object.

“The light radiated from a body gives that body a little push. The warmer side of an asteroid pushes a little harder than the cooler side because the warmer side emits more light (in invisible infrared wavelengths), so there is a net non-gravitational force acting on the body “, explained Tholen, co-discoverer of Apophis. “It’s such a small force that you don’t notice in larger objects, but the smaller the object, the easier it is to detect the effect.”

Tholen and his colleagues have been tracking Apophis’ position for the past 16 years and have now noticed a slight deviation from an orbital path limited solely by gravity.

“The observations made with Subaru in January and March of this year were critical to the success of this effort, as they allowed us to measure the position of the asteroid with an accuracy of about twice the size of the asteroid itself,” he said. “Apophis is about 300 meters in diameter and we measured the position at about 700 meters, even though we were about 70 million kilometers from the object.”

His team’s calculations show that the semi-major axis (half the longest length of an elliptical orbit) of Apophis’s orbit is currently shrinking at a speed of about 170 meters each year due to the Yarkovsky effect and not due to of gravity. When Apophis passes Earth in 2029, its semi-major axis will increase significantly due to our planet’s gravity, he said.

Further observations should improve the estimates, including better characterization of how the Yarkovsky effect is affecting the Apophis drift rate. It’s safe enough to say that astronomers will know if an impact is inevitable long before 2068.

In case you are wondering, the two near-Earth objects with the highest risk scores on the Palermo Technical Impact Hazard scale are the asteroid. 29075 (1950 DA) and the asteroid Determinant 9075. (1950 DA) with a probability of 1 in 8300 (0,012%) of hitting Earth in 2880 and Bennu, which is currently underway investigated from NASA’s OSIRIS-REx spacecraft, has a probability of 1 inch 2700 (0,037%) of an impact on the ground between the years 2175 and 2199. There are objects with a greater probability of impact on us, but the Palermo scale takes into account other factors, such as the possibility of an asteroid causing catastrophic damage.