This is the Guardian.

This week presents a once in a lifetime opportunity.

It's a celestial visitor that hasn't passed through these parts since Neanderthals walk the earth.

A rare green comet will make its closest approach to Earth for 50,000 years. The catchally named C-2020-2 E3 ZTF should be most visible tomorrow, the 1st of February.

And after its orbit close to Earth, it likely won't come back into orbit for several million years.

But it coincides with new research, highlighting the devastating impact of light pollution on our night skies.

The number of stars we can see with the naked eye

has reduced dramatically because of light pollution or sky glow.

So what's the best way to see the comet and how skyglow changing our relationship with the night sky?

From the Guardian I mean sample and this is Science Weekly.

Dr Stuart Clark, you're an astronomy journalist and Starwatch columnist columnist for The Guardian. First of all, tell me about this green comet. Where's it been? Where will it be going next?

This is a comet that spends most of its time far, far out in the most distant reaches of the solar system in a place called the

aort cloud which is this huge reservoir of ancient comets and because they're on such huge orbits they spend most of their time out there but

periodically they come close to the sun.

I have to ask why is it green it has this sort of quite subtle green glow about it.

That glow is coming from molecules of carbon.

When the carbon molecules are excited by the ultraviolet radiation that's coming from the sun that processes that

energy and gives it back out as green light. How close is this comet going to come to Earth?

And is there anything astronomers can learn from

comets when they do come this close to Earth?

Yeah, so we're looking at an approach distance of about 27 million miles and when these ancient comets fall in

you know from the outer solar system they've been pretty much untouched since the formation of the solar system 4.6 billion years ago.

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