NASA reveals the reality behind asteroid’s comet-like tail

A recent discovery about asteroid 3200 Phaethon, which is responsible for the annual Geminid meteor shower, has surprised astronomers and challenged the understanding of this celestial object so far. While asteroids are typically made up of rocky material and do not form tails when approaching the Sun, this asteroid behaves like a comet, brightening and forming a tail as it gets closer to the Sun.

For years, scientists believed that dust escaping from the asteroid was responsible for its comet-like feature. However, a new study using two NASA solar observatories has revealed that Phaethon's tail is primarily composed of sodium gas rather than dust. This suggests that the vaporisation of sodium within the asteroid as it comes into close proximity with the Sun drives its comet-like behaviour.

According to the official website of NASA, Qicheng Zhang, a PhD student at the California Institute of Technology who led the new study into Phaethon, stated that the asteroid's activity cannot be explained by any kind of dust. In 2009, NASA's Solar Terrestrial Relations Observatory (STEREO) spotted a short tail extending from the asteroid, supporting the idea that dust was escaping the asteroid's surface when heated by the Sun. The trail, however, contains far more material than Phaethon could have reasonably shed during its close encounters to the Sun, according to observations made by NASA's Parker Solar Probe in 2018.