This Friday, the asteroid named after the Egyptian god of chaos becomes visible from Earth (fortunately, not with the naked eye): Apophis will cross the Earth’s trajectory, but without danger of colliding with the planet – at least, no this time. It will be at 0.11 AU (an astronomical unit is the distance between the Earth and the Sun) or 150 million kilometers, 44 times the distance between us and the Moon.
However, each time it comes back around the Sun, that distance decreases. Today, it is, at the furthest point from us, 2 AU and, therefore, the Apophis (actually 99942 Apophis) is classified as an asteroid “Atens”, a group that gathers those whose orbits are smaller in width than the width of the Earth’s orbit, or 1 AU.
In 2029, however, he will expand his trajectory and, therefore, he will be promoted to another group, known as “Apollo”, of asteroids whose orbit is larger than 1 AU – these are considered more dangerous. Even when scraping through the high-altitude satellite zone, it will not hit the Earth – the same was already predicted for the passage of the Apophis in 1936.
The problem is that nothing is certain about this asteroid (in fact, none of them). The sunlight itself has the ability to alter its trajectories, as well as the Earth’s gravity. So while this year’s flyby will be used as an exercise for astronomers and astrophysicists who are part of the planetary defense system, the passage of the asteroid in 2029 will be a unique opportunity.
A decade of preparation
“We already know that this encounter with Earth will affect Apophis’s orbit, but our models also show that the approach may change the way this asteroid rotates, and it is possible that there will be some changes on the surface, such as small avalanches,” he said, during the Planetary Defense Conference in April 2019, astronomer Davide Farnocchia, from the Center for the Study of Near-Earth Objects (CNEOS) at NASA’s Jet Propulsion Laboratory.
At the time and ten years in advance, a plan began to be drafted to extract as much information about Apophis when it becomes visible to the naked eye – including the possibility of sending a probe to it, for the collection of material and study of its interior.
“Apophis is a representative of about two thousand Potentially Hazardous Asteroids, or PHAs, currently known. By observing it during its 2029 flyby, we will gain important scientific knowledge that could one day be used for planetary defense, ”said Paul Chodas, director of CNEOS.
One of the aspects that could be better observed this year is the shape of the Apophis (images captured by the late Arecibo Radio Telescope showed that it has the shape of a giant peanut). He would be the age of the solar system (about 4.6 billion), wandering between planets ever since and being pushed back and forth by the gravitational influence mainly of Jupiter.
The approach of an asteroid is the opportunity for the astronomical community to investigate, using radio telescopes, the shape and rotation of the asteroids. This year, that task will not be Arecibo’s, but NASA’s Goldstone Deep Space Communications Complex in California.
Since the last Wednesday (3) your antennas are directed to follow the Apophis, a mission that will be completed until the next 14th, when the asteroid will no longer be in reach. Who will take on the task of following the messenger of chaos will be the NEOWISE space telescope – at least, until the end of April.