Although a blue moon has nothing to do with color, the same can’t be said for asteroids.
An international team studying 3200 Phaethon, a 3.6-mile-long rock believed responsible for the annual Geminid meteor shower, has revealed that the asteroid’s surface exhibits a blue color. First discovered 1983, Phaethon has long been considered a “dead comet” based on its eccentric orbit, a characteristic that brings it closer to the sun than any other known asteroid. The fact that it’s blue, however — a color that defines only a fraction of known asteroids and never a comet — has the team once more stumped on Phaethon’s true identity.
“At the time, the assumption was that Phaethon probably was a dead, burnt-out comet,” team leader Teddy Kareta, a graduate student at the University of Arizona, said in a statement, “but comets are typically red in color, and not blue. So, even though Phaeton’s highly eccentric orbit should scream ‘dead comet,’ it’s hard to say whether Phaethon is more like an asteroid or more like a dead comet.”
The research team was able to discover new insights about Phaethon after training telescopes in Hawaii and Alaska on it during a close flyby of Earth in December 2017. It then continued on its orbital path around the sun (a circuit that typically takes just over 1.4 years to complete) where it experienced temperatures exceeding 1,500 degrees Fahrenheit (815 Celsius) — hot enough to melt aluminum.