Ceres
Phaethon is now around half the size of the Chicxulub asteroid that wiped out the dinosaur population on Earth ESA/ATG medialab

A massive asteroid is expected to zoom past Earth in a particularly close encounter in December, according to Russian astronomers at the Immanuel Kant Baltic Federal University. The asteroid – (3200) Phaethon – has been named after the Greek demigod Phaethon, who according to legend, was once allowed to ride the sun chariot for a day.

The 5km-wide asteroid is expected to fly past Earth mere days before Christmas, on 17 December at a distance of a mere 10 million kms away. The giant asteroid will be accompanied by the Geminids meteor shower, which is also expected to occur in mid-December.

According to Russian astronomers, the asteroid was once even bigger. The Daily Mail reports that Phaethon is now around half the size of the Chicxulub asteroid that wiped out the dinosaur population on Earth. However, the asteroid's many close approaches to the Sun are believed to have caused it to crumble into smaller pieces.

"Apparently, once it was a larger object, but multiple approaches to the Sun crushed it into many small debris that formed this stream. In this case, the asteroid itself can be the remains of a cometary nucleus," astronomers at the Immanuel Kant Baltic Federal University said in a statement.

The Phaethon asteroid has had several encounters with Earth in the past. However, it continues to puzzle astronomers as it reportedly has features of both a comet and an asteroid. During a previous flyby, scientists observed dust streaming from the object that looked like the melting ice tails usually seen on comets.

However, Phaethon's orbit indicates that it originates from the space between Mars and Jupiter – an area known to be populated with asteroids.