An astronomer from the University of Hawaii’s Institute of Astronomy (IfA) has published critical new findings linked to the asteroid Apophis. Dave Tholen and collaborators have detected Yarkovsky acceleration of Apophis, increasing the possibility of an impact with Earth in 2068.
Yarkovsky acceleration arises from an extremely weak force acting on an object in space due to non-uniform thermal radiation. The magnitude of the force and thus the acceleration is dependant on many factors. Factors include the exact shape of the asteroid, its orientation, and its measure of diffuse reflection of solar radiation.
Asteroids maintain a thermal equilibrium by reradiating the energy they absorb from sunlight in the form of heat. This process causes a slight change in their orbits. Yarkovsky’s effect is most significant for meteoroids and small asteroids of about 10cm to 10Kms in diameter.
Astronomers had earlier ruled out the possibility of an Earth impact in 2068 for Apophis. Now the detection of Yarkosvsky acceleration makes the 2068 impact a possibility. The team’s findings are presented in a paper at the 2020 virtual meeting of the Division for Planetary Sciences of the American Astronomical Society.
Apophis, a 370 meter-sized asteroid, will make a close approach to Earth on Friday, April 13, 2029. It will be visible to the naked eye as it passes within the Earth’s communications satellite belt.
Tholen said, “The new observations we obtained with the Subaru telescope earlier this year were good enough to reveal the Yarkovsky acceleration of Apophis, and they show that the asteroid is drifting away from a purely gravitational orbit by about 170 meters per year, which is enough to keep the 2068 impact scenario in play.” Tholen has been accurately tracking the motion of the Apophis since his team discovered it in 2004.
The co-author of the paper, Davide Farnocchia from the Jet Propulsion Laboratory, performed Apophis’s orbital calculations.
Further observations are underway to refine the impact of the Yarksovky effect on Apophis’s orbit. Well before 2068, astronomers will know if there is a slight chance of impact.
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