Of the few known space objects that pose a threat to Earth, one of the most followed by researchers is Apophis – and new calculations indicate that it still has the potential to collide with our planet. From observations made with the Subaru telescope, scientists are dedicated to analyzing an effect called Yarkovsky, which acts as a propulsion system integrated with the celestial body and generates small deviations in its orbit. Dave Tholen, from the University of Hawaii, is adamant about what he can do: “With this change, the probability is small, but not non-existent.”
The findings were described in an article presented during the 2020 virtual meeting of the American Astronomical Society’s Division of Planetary Sciences. According to the analysis, Apophis is the 3rd biggest danger (when talking about what comes from outside), with 1 chance in 150 thousand that he will really clash with us on April 12, 2068 – 0.00067%. It may be even lower, according to the NEODyS impact monitor, which includes a Yarkovsky nominal rate of change (1 in 530 thousand).
Anyway, Tholen warns that it is necessary to be careful with very positive estimates, since other variables must be considered. In the worst case scenario, formed by nickel and iron, measuring more than 300 meters wide (three football fields), its impact would release the equivalent of a 1,151-megaton TNT bomb – an event that occurs once every 80,000 years over here.
Expectations were already worse, because when discovered in 2004, experts projected a 2.7% chance that Apophis would land in our home. However, everything changes all the time, as asteroids are directly exposed to sunlight, absorbing energy and redirecting heat to the Universe, which results in increased speeds and changes in their trajectories.
“The light radiated from a body gives it a small, tiny push. The warmer side of an asteroid pushes a little harder than the cooler side, because the warmer side emits more light (at invisible infrared wavelengths ), so there is a non-gravitational force acting on the body, “explained Tholen, who has been paying special attention to the rock for 16 years with his team. “It is such a small force that it is not noticeable for larger objects, but the smaller the object, the easier it is to detect the effect,” he added. In addition, the gravitational power, of course, must be taken into account.
Observations carried out in January and March provided the necessary details for the new predictions and, when Apophis approaches Earth in 2029, our planet will have an influence on him. So, 9 years from now, we can have a better idea if the end, at least this one, is near.