Exotic green comet not seen since stone age returns to skies above Earth

An exotic green comet that has not passed Earth since the time of the Neanderthals has reappeared in the sky ready for its closest approach to the planet next week. Discovered last March by astronomers at the Zwicky Transient Facility at the Palomar Observatory in California, comet C/2022 E3 (ZTF) was calculated to orbit the sun every 50,000 years, meaning it last tore past our home planet in the stone age.

Comet C/2022 E3 (ZTF) could be visible to the naked eye as it whizzes past Earth, astronomers have said. Photograph: Dan Bartlett/Nasa/AFP/Getty Images

The comet, which comes from the Oort cloud at the edge of the solar system, will come closest to Earth on Wednesday and Thursday next week when it shoots past the planet at a distance of 2.5 light minutes – a mere 27m miles…