Artwork of the asteroid 3200 Phaethon. Phaethon is an Apollo asteroid - that is, its orbit crosses the Earth's although generally it is further from the Sun than our planet. It is a potential hazard to life on Earth. Phaethon approaches the Sun more closely than any other named asteroid, at just 0.14 astronomical units, or half of Mercury's closest approach. In 2010, Phaethon was observed emitting jets of dust, possibly from fractures caused by excessive heating as it approaches the Sun. Other asteroids have also been found which, like Phaeton, exhibit both asteroid and comet-like features. They have been dubbed 'active asteroids'.