In 2017 we knew that the gigantic asteroid full of nickel and iron of about 400 meters wide, 99942 Apophis, had a probability of 1 in 100,000 of hitting the Earth; considered, therefore, a real threat against our planet. Now, an astronomer at the Institute of Astronomy (IfA) at the University of Hawaii has made a new discovery related precisely to its trajectory that is expected to pass very close to Earth . The asteroid is accelerating, gaining speed, due to the Yarkovsky effect, due to an extremely weak force on the object due to non-uniform thermal radiation. This new data affects the probability of a land impact in 2068, as it can cause a non-gravitational deflection that leads it to an impact trajectory against us, although the possibilities are still very small.
Apophis was discovered in 2004 . Initially, it appeared that the rock might crash into Earth on April 13, 2029, or perhaps April 2036. More precise observations later revealed that in both cases, the chance of an actual impact was zero, although the 2029 flyby it will take Apophis within the orbits of the geostationary satellites; it will be visible as an object with the naked eye moving rapidly from Europe and Africa.
Thus, the scientists claimed that the impact was impossible, but this new finding suggests that the asteroid has a chance of crashing into Earth on April 12, 2068, a scenario that could be catastrophic for our planet, as it would do so with the force of 1,151 megatons of TNT.
The possible scenario
The Yarkovsky effect, on which this prediction is based, is a subtle net force on a small, rotating body caused by asymmetric heating. Scientists measured the strength of this effect on Apophis by making extremely precise positional observations using the Japanese Subaru 8.3-meter telescope on Mauna Kea. Their results indicate that the semi-major axis of the asteroid’s orbit is decreasing 170 meters per year. The result: there is a slim chance (currently around 1 in 150,000) of an actual impact in April 2068 . At its closest point in 2029, Apophis will pass only 37,725 km from our planet, or about 10% of the Earth-Moon distance.
And is that all asteroids need to re-radiate as heat the energy they absorb from sunlight to maintain thermal balance, a process that slightly changes the orbit of the asteroid.
Tholen, who has been tracking the motion of Apophis in the sky since he and his colleagues discovered it at the Kitt Peak National Observatory near Tucson, Arizona on June 19, 2004, commented: “We have known for some time that a Impact with Earth is not possible during the close approach of 2029. The new observations we obtained with the Subaru telescope earlier this year were consistent enough to reveal the Yarkovsky acceleration of Apophis, and show that the asteroid is moving away from a purely gravitational orbit at about 170 meters per year, which is enough to keep the 2068 impact scenario in play ”.
NASA and other space agencies are constantly monitoring potentially dangerous objects for these orbit-altering effects. This is a critical factor in the case of asteroids like Apophis, which are programmed to pass very close to Earth. Fortunately, we are preparing for this possible scenario. The DART mission, for example, will conduct a dress rehearsal in 2021 in which a small spacecraft will crash into a small asteroid in an attempt to deflect it from its course. It’s just a test, but it will offer space agencies around the world a wealth of data that could be used to create a deterrent for asteroids that may be on a collision course with Earth.
As a curiosity, on the night of March 5, 2021, the huge space rock will pass 16,852,369 km from our planet, that is, approximately 44 times the distance to the Moon, a moment that astronomers will take advantage of to study it and be able to get more observations details of this asteroid.
To observe it with the naked eye, something that almost never happens with asteroids, we will have to wait until April 13, 2029. According to NASA, Apophis will be seen as a speck of light moving through Australia; it will be over the Atlantic Ocean at its closest approach to Earth and it will move so fast that it will cross this ocean in just one hour.
Reference: University of Hawaii
