Phaethon Spied During Close Earth Approach

The asteroid responsible for the Geminid meteor shower which takes place every December, 3200 Phaethon, made its closest passing through the vicinity of the planet Earth since its discovery in 1983. The event, which took place on the 10th of December last year, was anticipated by the Arecibo Observatory, which pointed its telescope towards the cosmic object on December 8.

Most of the meteor showers which take place on Earth are generated by comets spreading debris as they come through the inner regions of the solar system. This seems not to be the case with the Geminid anyway. Originating from a point in the sky in the Gemini constellation, the Geminid meteor shower is one of the most satisfying annual meteor showers.

After more than six months of inactivity, when it received a new coat of paint, the Areciebo Observatory focused on the 3200 Phaethon asteroid on its path around the Sun, that took it only 18 million kilometers from Earth and two time close to the Sun than planet Mercury. All asteroids ranging from 10 centimeters to 10 kilometers in diameter have orbits greatly altered by the action of the solar wind, through a process called the Yarkovsky effect, caused by anisotropic emissions of thermal photons.

In order to understand the changes in the motion of these asteroids, the Arecibo radar telescope conducted a series of measurements on Phaethon's properties. The asteroids coming in the inner regions of the solar system are affected not only by solar wind, but by sunlight, the shape of the Sun and some other relativity effects as well.

After the paint project ended in November last year, the first of its kind in more than 40 years, the maintenance crew from Arecibo worked around the clock in order to prepare the 300 meter radio telescope for the December observations. Currently, the telescope, based in Puerto Rico and operated by NASA, is fully functionally and awaiting more than a dozen projects which are to take place in the following months.