The blue color of the Phaeton asteroid has bothered scientists since its discovery in the early 1980s. In a new study, they suggested that the blue hue is associated with a specific orbit of the stone.
The phaeton moves around the Sun in an elliptical orbit, making it closer to the star than any other known asteroid. And although this convergence is short-lived, and after that Phaeton recedes behind the Mars orbit, the intensity of solar radiation to which the asteroid is exposed during these flights is sufficient to gradually clean its surface from red chemicals that astronomers observe in asteroids away from the sun.
During its close passages, the Phaeton is at a distance of 21 million km from the Sun. This is three times closer to the Sun than the orbit of Mercury. As the Phaeton approaches the star, the asteroid’s surface heats up to 800°C. A new study suggests that this heat triggers a chain of chemical reactions that evaporate iron-rich substances and red organic compounds.
According to researchers, there are only a few dozen blue asteroids in the solar system, but the Phaeton is the most blue of them all. Interestingly, several other comets approaching the Sun also have a pronounced blue color.
Scientists have modeled in detail the chemical composition of the Phaeton’s surface and calculated what happens to these chemicals when the asteroid’s temperature changes in its orbit. According to them, the conversion of carbon into soot at high temperatures near the Sun may also contribute to the appearance of the brand blue color of the Phaeton.
Scientists will be able to find out the accuracy of their assumptions in a few years, as the Japan Aerospace Exploration Agency plans to send the DESTINY+ orbiter to study the Phaeton.