Move over Hale-Bopp: Once in 50,000-year comet may be visible to naked eye

The celestial object is catchily called C/2022 E3 (ZTF) – after the Zwicky Transient Facility – which first spotted it passing Jupiter in March last year.

After travelling from the icy reaches of our Solar System it will come closest to the Sun on 12 January and pass nearest to Earth on 1 February.

Astronomers say tt will be easy to spot with a good pair of binoculars and even with the naked eye, provided the sky is not too illuminated by city lights or the Moon.

According to Thomas Prince, a physics professor at the California Institute of Technology, the comet "will be brightest when it is closest to the Earth."

Made of ice and dust and emitting a greenish aura, the comet is estimated to have a diameter of around one kilometre, said Nicolas Biver, an astrophysicist at the Paris Observatory.

That makes it significantly smaller than NEOWISE, the last comet visible with an unaided eye, which passed Earth in March 2020, and Hale-Bopp, which swept by in 1997 with a potentially life-ending diameter of around 60 kilometres.

However, the newest visit will come closer to Earth, which "may make up for the fact that it is not very big", Biver said.

While the comet will be brightest as it passes Earth in early February, a fuller moon could make spotting it difficult.

The new moon during the weekend of 21-22 January offers a good chance for stargazers.

"We could also get a nice surprise and the object could be twice as bright as expected," Biver added.

'Rare visitor'

The comet has apparently spent most of its life "at least 2,500 times more distant than the Earth is from the Sun", according to Prince.

Biver said the comet is believed to have come from the Oort Cloud – a theorised vast sphere surrounding the Solar System – that is home to mysterious icy objects.

The last time this comet passed Earth was during the Upper Paleolithic period, when Neanderthals still roamed Earth.

Prince said the comet's next visit to the inner Solar System is expected in another 50,000 years.

But Biver said there was a possibility that after this visit the comet will be "permanently ejected from the Solar System".

Among those closely watching will be the James Webb Space Telescope.

However, it will not take images, instead studying the comet's composition.

The closer the comet is to Earth, the easier it is for telescopes to measure its composition "as the Sun boils off its outer layers," Prince said.

This "rare visitor" will give "us information about the inhabitants of our Solar system well beyond the most distant planets", he added.

(with AFP)