A massive, 5km-wide asteroid will skim past Earth today (16 December), coming within 10 million kilometres of our planet. While this may seem far away, in astronomical terms its a pretty close call.
It has been classed as a Potentially Hazardous Asteroid, although this does not mean that there is a threat of an impact in the foreseeable future.
The object – known as (3200) Phaethon – is named after the son of the Greek Sun god Helion because its orbit brings it closer to the star than any other named asteroid.
Phaethon was first detected in 2007 and is widely thought to be the parent body for the Geminid meteor shower, which peaked earlier this week.
The object continues to puzzle astronomers because it has features of both a comet and an asteroid. Asteroids are usually made up of metals and rocky materials, whereas comets consist of ice, dust and rocky materials. Comets also form a tail when the ice vaporises as they approach the Sun.
Phaethon appears more like an asteroid, but occasionally it displays comet-like activity, leading some scientists to suggest it is actually an inactive comet nucleus.
Today's approach will be the closest it has come to Earth since 1974, with the asteroid expected to come nearest to our planet at 23:00 GMT. It will not make another approach as close as this until after 2093.
Nasa say that Phaethon will be visible through small telescopes in areas with little light pollution. It will be at its brightest until December 21.