Closely approaching the Sun, the asteroid Phaeton heats up, and in its depths the evaporation of sodium begins, which makes it brighter and makes it eject debris.
The six-kilometer near-Earth asteroid (3200) Phaethon is considered the source of the Geminid meteor shower, which comes to Earth in December. It moves around the Sun in a highly elongated orbit, completing a full revolution in 524 days. During this time, the asteroid manages to move far beyond the orbit of Mars, and approach the Sun twice as close to Mercury.
During the periods of approach to the star, the surface of Phaeton heats up to temperatures above 700 ° C, active evaporation of matter begins from it, so the asteroid is seen much brighter. There is no water ice on it, and sodium is believed to provide this activity. On the other hand, observations of the spectrum of the Geminid shower meteorites burning in the earth's atmosphere show that sodium is practically absent in it. A solution to this paradox was found by Joseph Masiero and his colleagues at the California Institute of Technology (Caltech), whose article was published in the Planetary Science Journal.
Scientists used computer models, and then - and real experiments with samples of a meteorite similar to Phaeton, which were heated, simulating the approach to the Sun. It turned out that under such conditions, the outer layers of the asteroid can quickly lose almost all of the sodium. However, heat penetrates inside and causes it to evaporate from the depths.
The vapor pressure increases, and with the extremely weak gravity of Phaeton, it quickly turns out to be enough for the gases not only to escape outward, but also throw out a mass of fine dust and debris from the surface with them. Thus, it is sodium that can serve as the basis for the activity of Phaethon when approaching the Sun, as well as the appearance of a stream of meteors, which themselves turn out to be poor in this element.